🛡
ArbPad Token ✨

To create a transparent ecosystem of DeFi services by leveraging on-chain transactions with know-your-customer (KYC) regulations. This will allow users to participate not only in late-stage IDO deals.
Category: Launchpad
Networks: Arbitrum Network
Website: https://www.arbpad.tech/​
Smart Contract Details
Team KYC
Audit Certificate
Links
Token Name: ArbPad
Token Ticker: ABP
Contract Address:  0xc6A69ad47B79097CC5155c46cafa55011ad4aeeD
1
// SPDX-License-Identifier: MIT
2
​
3
pragma solidity ^0.8.0;
4
​
5
// CAUTION
6
// This version of SafeMath should only be used with Solidity 0.8 or later,
7
// because it relies on the compiler's built in overflow checks.
8
​
9
/**
10
 * @dev Wrappers over Solidity's arithmetic operations.
11
 *
12
 * NOTE: `SafeMath` is generally not needed starting with Solidity 0.8, since the compiler
13
 * now has built in overflow checking.
14
 */
15
library SafeMath {
16
    /**
17
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
18
     *
19
     * _Available since v3.4._
20
     */
21
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
22
        unchecked {
23
            uint256 c = a + b;
24
            if (c < a) return (false, 0);
25
            return (true, c);
26
        }
27
    }
28
​
29
    /**
30
     * @dev Returns the subtraction of two unsigned integers, with an overflow flag.
31
     *
32
     * _Available since v3.4._
33
     */
34
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
35
        unchecked {
36
            if (b > a) return (false, 0);
37
            return (true, a - b);
38
        }
39
    }
40
​
41
    /**
42
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
43
     *
44
     * _Available since v3.4._
45
     */
46
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
47
        unchecked {
48
            // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
49
            // benefit is lost if 'b' is also tested.
50
            // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
51
            if (a == 0) return (true, 0);
52
            uint256 c = a * b;
53
            if (c / a != b) return (false, 0);
54
            return (true, c);
55
        }
56
    }
57
​
58
    /**
59
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
60
     *
61
     * _Available since v3.4._
62
     */
63
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
64
        unchecked {
65
            if (b == 0) return (false, 0);
66
            return (true, a / b);
67
        }
68
    }
69
​
70
    /**
71
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
72
     *
73
     * _Available since v3.4._
74
     */
75
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
76
        unchecked {
77
            if (b == 0) return (false, 0);
78
            return (true, a % b);
79
        }
80
    }
81
​
82
    /**
83
     * @dev Returns the addition of two unsigned integers, reverting on
84
     * overflow.
85
     *
86
     * Counterpart to Solidity's `+` operator.
87
     *
88
     * Requirements:
89
     *
90
     * - Addition cannot overflow.
91
     */
92
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
93
        return a + b;
94
    }
95
​
96
    /**
97
     * @dev Returns the subtraction of two unsigned integers, reverting on
98
     * overflow (when the result is negative).
99
     *
100
     * Counterpart to Solidity's `-` operator.
101
     *
102
     * Requirements:
103
     *
104
     * - Subtraction cannot overflow.
105
     */
106
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
107
        return a - b;
108
    }
109
​
110
    /**
111
     * @dev Returns the multiplication of two unsigned integers, reverting on
112
     * overflow.
113
     *
114
     * Counterpart to Solidity's `*` operator.
115
     *
116
     * Requirements:
117
     *
118
     * - Multiplication cannot overflow.
119
     */
120
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
121
        return a * b;
122
    }
123
​
124
    /**
125
     * @dev Returns the integer division of two unsigned integers, reverting on
126
     * division by zero. The result is rounded towards zero.
127
     *
128
     * Counterpart to Solidity's `/` operator.
129
     *
130
     * Requirements:
131
     *
132
     * - The divisor cannot be zero.
133
     */
134
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
135
        return a / b;
136
    }
137
​
138
    /**
139
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
140
     * reverting when dividing by zero.
141
     *
142
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
143
     * opcode (which leaves remaining gas untouched) while Solidity uses an
144
     * invalid opcode to revert (consuming all remaining gas).
145
     *
146
     * Requirements:
147
     *
148
     * - The divisor cannot be zero.
149
     */
150
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
151
        return a % b;
152
    }
153
​
154
    /**
155
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
156
     * overflow (when the result is negative).
157
     *
158
     * CAUTION: This function is deprecated because it requires allocating memory for the error
159
     * message unnecessarily. For custom revert reasons use {trySub}.
160
     *
161
     * Counterpart to Solidity's `-` operator.
162
     *
163
     * Requirements:
164
     *
165
     * - Subtraction cannot overflow.
166
     */
167
    function sub(
168
        uint256 a,
169
        uint256 b,
170
        string memory errorMessage
171
    ) internal pure returns (uint256) {
172
        unchecked {
173
            require(b <= a, errorMessage);
174
            return a - b;
175
        }
176
    }
177
​
178
    /**
179
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
180
     * division by zero. The result is rounded towards zero.
181
     *
182
     * Counterpart to Solidity's `/` operator. Note: this function uses a
183
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
184
     * uses an invalid opcode to revert (consuming all remaining gas).
185
     *
186
     * Requirements:
187
     *
188
     * - The divisor cannot be zero.
189
     */
190
    function div(
191
        uint256 a,
192
        uint256 b,
193
        string memory errorMessage
194
    ) internal pure returns (uint256) {
195
        unchecked {
196
            require(b > 0, errorMessage);
197
            return a / b;
198
        }
199
    }
200
​
201
    /**
202
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
203
     * reverting with custom message when dividing by zero.
204
     *
205
     * CAUTION: This function is deprecated because it requires allocating memory for the error
206
     * message unnecessarily. For custom revert reasons use {tryMod}.
207
     *
208
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
209
     * opcode (which leaves remaining gas untouched) while Solidity uses an
210
     * invalid opcode to revert (consuming all remaining gas).
211
     *
212
     * Requirements:
213
     *
214
     * - The divisor cannot be zero.
215
     */
216
    function mod(
217
        uint256 a,
218
        uint256 b,
219
        string memory errorMessage
220
    ) internal pure returns (uint256) {
221
        unchecked {
222
            require(b > 0, errorMessage);
223
            return a % b;
224
        }
225
    }
226
}
227
​
228
​
229
​
230
​
231
pragma solidity ^0.8.0;
232
​
233
/**
234
 * @dev Provides information about the current execution context, including the
235
 * sender of the transaction and its data. While these are generally available
236
 * via msg.sender and msg.data, they should not be accessed in such a direct
237
 * manner, since when dealing with meta-transactions the account sending and
238
 * paying for execution may not be the actual sender (as far as an application
239
 * is concerned).
240
 *
241
 * This contract is only required for intermediate, library-like contracts.
242
 */
243
abstract contract Context {
244
    function _msgSender() internal view virtual returns (address) {
245
        return msg.sender;
246
    }
247
​
248
    function _msgData() internal view virtual returns (bytes calldata) {
249
        return msg.data;
250
    }
251
}
252
​
253
​
254
​
255
​
256
pragma solidity ^0.8.0;
257
​
258
/**
259
 * @dev Contract module which provides a basic access control mechanism, where
260
 * there is an account (an owner) that can be granted exclusive access to
261
 * specific functions.
262
 *
263
 * By default, the owner account will be the one that deploys the contract. This
264
 * can later be changed with {transferOwnership}.
265
 *
266
 * This module is used through inheritance. It will make available the modifier
267
 * `onlyOwner`, which can be applied to your functions to restrict their use to
268
 * the owner.
269
 */
270
abstract contract Ownable is Context {
271
    address private _owner;
272
​
273
    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
274
​
275
    /**
276
     * @dev Initializes the contract setting the deployer as the initial owner.
277
     */
278
    constructor() {
279
        _transferOwnership(_msgSender());
280
    }
281
​
282
    /**
283
     * @dev Returns the address of the current owner.
284
     */
285
    function owner() public view virtual returns (address) {
286
        return _owner;
287
    }
288
​
289
    /**
290
     * @dev Throws if called by any account other than the owner.
291
     */
292
    modifier onlyOwner() {
293
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
294
        _;
295
    }
296
​
297
    /**
298
     * @dev Leaves the contract without owner. It will not be possible to call
299
     * `onlyOwner` functions anymore. Can only be called by the current owner.
300
     *
301
     * NOTE: Renouncing ownership will leave the contract without an owner,
302
     * thereby removing any functionality that is only available to the owner.
303
     */
304
    function renounceOwnership() public virtual onlyOwner {
305
        _transferOwnership(address(0));
306
    }
307
​
308
    /**
309
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
310
     * Can only be called by the current owner.
311
     */
312
    function transferOwnership(address newOwner) public virtual onlyOwner {
313
        require(newOwner != address(0), "Ownable: new owner is the zero address");
314
        _transferOwnership(newOwner);
315
    }
316
​
317
    /**
318
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
319
     * Internal function without access restriction.
320
     */
321
    function _transferOwnership(address newOwner) internal virtual {
322
        address oldOwner = _owner;
323
        _owner = newOwner;
324
        emit OwnershipTransferred(oldOwner, newOwner);
325
    }
326
}
327
​
328
​
329
​
330
​
331
pragma solidity ^0.8.0;
332
​
333
/**
334
 * @dev Interface of the ERC20 standard as defined in the EIP.
335
 */
336
interface IERC20 {
337
    /**
338
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
339
     * another (`to`).
340
     *
341
     * Note that `value` may be zero.
342
     */
343
    event Transfer(address indexed from, address indexed to, uint256 value);
344
​
345
    /**
346
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
347
     * a call to {approve}. `value` is the new allowance.
348
     */
349
    event Approval(address indexed owner, address indexed spender, uint256 value);
350
​
351
    /**
352
     * @dev Returns the amount of tokens in existence.
353
     */
354
    function totalSupply() external view returns (uint256);
355
​
356
    /**
357
     * @dev Returns the amount of tokens owned by `account`.
358
     */
359
    function balanceOf(address account) external view returns (uint256);
360
​
361
    /**
362
     * @dev Moves `amount` tokens from the caller's account to `to`.
363
     *
364
     * Returns a boolean value indicating whether the operation succeeded.
365
     *
366
     * Emits a {Transfer} event.
367
     */
368
    function transfer(address to, uint256 amount) external returns (bool);
369
​
370
    /**
371
     * @dev Returns the remaining number of tokens that `spender` will be
372
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
373
     * zero by default.
374
     *
375
     * This value changes when {approve} or {transferFrom} are called.
376
     */
377
    function allowance(address owner, address spender) external view returns (uint256);
378
​
379
    /**
380
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
381
     *
382
     * Returns a boolean value indicating whether the operation succeeded.
383
     *
384
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
385
     * that someone may use both the old and the new allowance by unfortunate
386
     * transaction ordering. One possible solution to mitigate this race
387
     * condition is to first reduce the spender's allowance to 0 and set the
388
     * desired value afterwards:
389
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
390
     *
391
     * Emits an {Approval} event.
392
     */
393
    function approve(address spender, uint256 amount) external returns (bool);
394
​
395
    /**
396
     * @dev Moves `amount` tokens from `from` to `to` using the
397
     * allowance mechanism. `amount` is then deducted from the caller's
398
     * allowance.
399
     *
400
     * Returns a boolean value indicating whether the operation succeeded.
401
     *
402
     * Emits a {Transfer} event.
403
     */
404
    function transferFrom(
405
        address from,
406
        address to,
407
        uint256 amount
408
    ) external returns (bool);
409
}
410
​
411
​
412
​
413
​
414
pragma solidity ^0.8.0;
415
​
416
/**
417
 * @dev Interface for the optional metadata functions from the ERC20 standard.
418
 *
419
 * _Available since v4.1._
420
 */
421
interface IERC20Metadata is IERC20 {
422
    /**
423
     * @dev Returns the name of the token.
424
     */
425
    function name() external view returns (string memory);
426
​
427
    /**
428
     * @dev Returns the symbol of the token.
429
     */
430
    function symbol() external view returns (string memory);
431
​
432
    /**
433
     * @dev Returns the decimals places of the token.
434
     */
435
    function decimals() external view returns (uint8);
436
}
437
​
438
​
439
​
440
​
441
pragma solidity ^0.8.0;
442
​
443
​
444
​
445
/**
446
 * @dev Implementation of the {IERC20} interface.
447
 *
448
 * This implementation is agnostic to the way tokens are created. This means
449
 * that a supply mechanism has to be added in a derived contract using {_mint}.
450
 * For a generic mechanism see {ERC20PresetMinterPauser}.
451
 *
452
 * TIP: For a detailed writeup see our guide
453
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
454
 * to implement supply mechanisms].
455
 *
456
 * We have followed general OpenZeppelin Contracts guidelines: functions revert
457
 * instead returning `false` on failure. This behavior is nonetheless
458
 * conventional and does not conflict with the expectations of ERC20
459
 * applications.
460
 *
461
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
462
 * This allows applications to reconstruct the allowance for all accounts just
463
 * by listening to said events. Other implementations of the EIP may not emit
464
 * these events, as it isn't required by the specification.
465
 *
466
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
467
 * functions have been added to mitigate the well-known issues around setting
468
 * allowances. See {IERC20-approve}.
469
 */
470
contract ERC20 is Context, IERC20, IERC20Metadata {
471
    mapping(address => uint256) private _balances;
472
​
473
    mapping(address => mapping(address => uint256)) private _allowances;
474
​
475
    uint256 private _totalSupply;
476
​
477
    string private _name;
478
    string private _symbol;
479
​
480
    /**
481
     * @dev Sets the values for {name} and {symbol}.
482
     *
483
     * The default value of {decimals} is 18. To select a different value for
484
     * {decimals} you should overload it.
485
     *
486
     * All two of these values are immutable: they can only be set once during
487
     * construction.
488
     */
489
    constructor(string memory name_, string memory symbol_) {
490
        _name = name_;
491
        _symbol = symbol_;
492
    }
493
​
494
    /**
495
     * @dev Returns the name of the token.
496
     */
497
    function name() public view virtual override returns (string memory) {
498
        return _name;
499
    }
500
​
501
    /**
502
     * @dev Returns the symbol of the token, usually a shorter version of the
503
     * name.
504
     */
505
    function symbol() public view virtual override returns (string memory) {
506
        return _symbol;
507
    }
508
​
509
    /**
510
     * @dev Returns the number of decimals used to get its user representation.
511
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
512
     * be displayed to a user as `5.05` (`505 / 10 ** 2`).
513
     *
514
     * Tokens usually opt for a value of 18, imitating the relationship between
515
     * Ether and Wei. This is the value {ERC20} uses, unless this function is
516
     * overridden;
517
     *
518
     * NOTE: This information is only used for _display_ purposes: it in
519
     * no way affects any of the arithmetic of the contract, including
520
     * {IERC20-balanceOf} and {IERC20-transfer}.
521
     */
522
    function decimals() public view virtual override returns (uint8) {
523
        return 18;
524
    }
525
​
526
    /**
527
     * @dev See {IERC20-totalSupply}.
528
     */
529
    function totalSupply() public view virtual override returns (uint256) {
530
        return _totalSupply;
531
    }
532
​
533
    /**
534
     * @dev See {IERC20-balanceOf}.
535
     */
536
    function balanceOf(address account) public view virtual override returns (uint256) {
537
        return _balances[account];
538
    }
539
​
540
    /**
541
     * @dev See {IERC20-transfer}.
542
     *
543
     * Requirements:
544
     *
545
     * - `to` cannot be the zero address.
546
     * - the caller must have a balance of at least `amount`.
547
     */
548
    function transfer(address to, uint256 amount) public virtual override returns (bool) {
549
        address owner = _msgSender();
550
        _transfer(owner, to, amount);
551
        return true;
552
    }
553
​
554
    /**
555
     * @dev See {IERC20-allowance}.
556
     */
557
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
558
        return _allowances[owner][spender];
559
    }
560
​
561
    /**
562
     * @dev See {IERC20-approve}.
563
     *
564
     * NOTE: If `amount` is the maximum `uint256`, the allowance is not updated on
565
     * `transferFrom`. This is semantically equivalent to an infinite approval.
566
     *
567
     * Requirements:
568
     *
569
     * - `spender` cannot be the zero address.
570
     */
571
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
572
        address owner = _msgSender();
573
        _approve(owner, spender, amount);
574
        return true;
575
    }
576
​
577
    /**
578
     * @dev See {IERC20-transferFrom}.
579
     *
580
     * Emits an {Approval} event indicating the updated allowance. This is not
581
     * required by the EIP. See the note at the beginning of {ERC20}.
582
     *
583
     * NOTE: Does not update the allowance if the current allowance
584
     * is the maximum `uint256`.
585
     *
586
     * Requirements:
587
     *
588
     * - `from` and `to` cannot be the zero address.
589
     * - `from` must have a balance of at least `amount`.
590
     * - the caller must have allowance for ``from``'s tokens of at least
591
     * `amount`.
592
     */
593
    function transferFrom(
594
        address from,
595
        address to,
596
        uint256 amount
597
    ) public virtual override returns (bool) {
598
        address spender = _msgSender();
599
        _spendAllowance(from, spender, amount);
600
        _transfer(from, to, amount);
601
        return true;
602
    }
603
​
604
    /**
605
     * @dev Atomically increases the allowance granted to `spender` by the caller.
606
     *
607
     * This is an alternative to {approve} that can be used as a mitigation for
608
     * problems described in {IERC20-approve}.
609
     *
610
     * Emits an {Approval} event indicating the updated allowance.
611
     *
612
     * Requirements:
613
     *
614
     * - `spender` cannot be the zero address.
615
     */
616
    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
617
        address owner = _msgSender();
618
        _approve(owner, spender, allowance(owner, spender) + addedValue);
619
        return true;
620
    }
621
​
622
    /**
623
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
624
     *
625
     * This is an alternative to {approve} that can be used as a mitigation for
626
     * problems described in {IERC20-approve}.
627
     *
628
     * Emits an {Approval} event indicating the updated allowance.
629
     *
630
     * Requirements:
631
     *
632
     * - `spender` cannot be the zero address.
633
     * - `spender` must have allowance for the caller of at least
634
     * `subtractedValue`.
635
     */
636
    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
637
        address owner = _msgSender();
638
        uint256 currentAllowance = allowance(owner, spender);
639
        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
640
        unchecked {
641
            _approve(owner, spender, currentAllowance - subtractedValue);
642
        }
643
​
644
        return true;
645
    }
646
​
647
    /**
648
     * @dev Moves `amount` of tokens from `sender` to `recipient`.
649
     *
650
     * This internal function is equivalent to {transfer}, and can be used to
651
     * e.g. implement automatic token fees, slashing mechanisms, etc.
652
     *
653
     * Emits a {Transfer} event.
654
     *
655
     * Requirements:
656
     *
657
     * - `from` cannot be the zero address.
658
     * - `to` cannot be the zero address.
659
     * - `from` must have a balance of at least `amount`.
660
     */
661
    function _transfer(
662
        address from,
663
        address to,
664
        uint256 amount
665
    ) internal virtual {
666
        require(from != address(0), "ERC20: transfer from the zero address");
667
        require(to != address(0), "ERC20: transfer to the zero address");
668
​
669
        _beforeTokenTransfer(from, to, amount);
670
​
671
        uint256 fromBalance = _balances[from];
672
        require(fromBalance >= amount, "ERC20: transfer amount exceeds balance");
673
        unchecked {
674
            _balances[from] = fromBalance - amount;
675
        }
676
        _balances[to] += amount;
677
​
678
        emit Transfer(from, to, amount);
679
​
680
        _afterTokenTransfer(from, to, amount);
681
    }
682
​
683
    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
684
     * the total supply.
685
     *
686
     * Emits a {Transfer} event with `from` set to the zero address.
687
     *
688
     * Requirements:
689
     *
690
     * - `account` cannot be the zero address.
691
     */
692
    function _mint(address account, uint256 amount) internal virtual {
693
        require(account != address(0), "ERC20: mint to the zero address");
694
​
695
        _beforeTokenTransfer(address(0), account, amount);
696
​
697
        _totalSupply += amount;
698
        _balances[account] += amount;
699
        emit Transfer(address(0), account, amount);
700
​
701
        _afterTokenTransfer(address(0), account, amount);
702
    }
703
​
704
    /**
705
     * @dev Destroys `amount` tokens from `account`, reducing the
706
     * total supply.
707
     *
708
     * Emits a {Transfer} event with `to` set to the zero address.
709
     *
710
     * Requirements:
711
     *
712
     * - `account` cannot be the zero address.
713
     * - `account` must have at least `amount` tokens.
714
     */
715
    function _burn(address account, uint256 amount) internal virtual {
716
        require(account != address(0), "ERC20: burn from the zero address");
717
​
718
        _beforeTokenTransfer(account, address(0), amount);
719
​
720
        uint256 accountBalance = _balances[account];
721
        require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
722
        unchecked {
723
            _balances[account] = accountBalance - amount;
724
        }
725
        _totalSupply -= amount;
726
​
727
        emit Transfer(account, address(0), amount);
728
​
729
        _afterTokenTransfer(account, address(0), amount);
730
    }
731
​
732
    /**
733
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
734
     *
735
     * This internal function is equivalent to `approve`, and can be used to
736
     * e.g. set automatic allowances for certain subsystems, etc.
737
     *
738
     * Emits an {Approval} event.
739
     *
740
     * Requirements:
741
     *
742
     * - `owner` cannot be the zero address.
743
     * - `spender` cannot be the zero address.
744
     */
745
    function _approve(
746
        address owner,
747
        address spender,
748
        uint256 amount
749
    ) internal virtual {
750
        require(owner != address(0), "ERC20: approve from the zero address");
751
        require(spender != address(0), "ERC20: approve to the zero address");
752
​
753
        _allowances[owner][spender] = amount;
754
        emit Approval(owner, spender, amount);
755
    }
756
​
757
    /**
758
     * @dev Updates `owner` s allowance for `spender` based on spent `amount`.
759
     *
760
     * Does not update the allowance amount in case of infinite allowance.
761
     * Revert if not enough allowance is available.
762
     *
763
     * Might emit an {Approval} event.
764
     */
765
    function _spendAllowance(
766
        address owner,
767
        address spender,
768
        uint256 amount
769
    ) internal virtual {
770
        uint256 currentAllowance = allowance(owner, spender);
771
        if (currentAllowance != type(uint256).max) {
772
            require(currentAllowance >= amount, "ERC20: insufficient allowance");
773
            unchecked {
774
                _approve(owner, spender, currentAllowance - amount);
775
            }
776
        }
777
    }
778
​
779
    /**
780
     * @dev Hook that is called before any transfer of tokens. This includes
781
     * minting and burning.
782
     *
783
     * Calling conditions:
784
     *
785
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
786
     * will be transferred to `to`.
787
     * - when `from` is zero, `amount` tokens will be minted for `to`.
788
     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
789
     * - `from` and `to` are never both zero.
790
     *
791
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
792
     */
793
    function _beforeTokenTransfer(
794
        address from,
795
        address to,
796
        uint256 amount
797
    ) internal virtual {}
798
​
799
    /**
800
     * @dev Hook that is called after any transfer of tokens. This includes
801
     * minting and burning.
802
     *
803
     * Calling conditions:
804
     *
805
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
806
     * has been transferred to `to`.
807
     * - when `from` is zero, `amount` tokens have been minted for `to`.
808
     * - when `to` is zero, `amount` of ``from``'s tokens have been burned.
809
     * - `from` and `to` are never both zero.
810
     *
811
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
812
     */
813
    function _afterTokenTransfer(
814
        address from,
815
        address to,
816
        uint256 amount
817
    ) internal virtual {}
818
}
819
​
820
​
821
​
822
​
823
pragma solidity ^0.8.0;
824
​
825
interface IUniswapV2Pair {
826
    event Approval(address indexed owner, address indexed spender, uint value);
827
    event Transfer(address indexed from, address indexed to, uint value);
828
​
829
    function name() external pure returns (string memory);
830
    function symbol() external pure returns (string memory);
831
    function decimals() external pure returns (uint8);
832
    function totalSupply() external view returns (uint);
833
    function balanceOf(address owner) external view returns (uint);
834
    function allowance(address owner, address spender) external view returns (uint);
835
​
836
    function approve(address spender, uint value) external returns (bool);
837
    function transfer(address to, uint value) external returns (bool);
838
    function transferFrom(address from, address to, uint value) external returns (bool);
839
​
840
    function DOMAIN_SEPARATOR() external view returns (bytes32);
841
    function PERMIT_TYPEHASH() external pure returns (bytes32);
842
    function nonces(address owner) external view returns (uint);
843
​
844
    function permit(address owner, address spender, uint value, uint deadline, uint8 v, bytes32 r, bytes32 s) external;
845
​
846
    event Mint(address indexed sender, uint amount0, uint amount1);
847
    event Burn(address indexed sender, uint amount0, uint amount1, address indexed to);
848
    event Swap(
849
        address indexed sender,
850
        uint amount0In,
851
        uint amount1In,
852
        uint amount0Out,
853
        uint amount1Out,
854
        address indexed to
855
    );
856
    event Sync(uint112 reserve0, uint112 reserve1);
857
​
858
    function MINIMUM_LIQUIDITY() external pure returns (uint);
859
    function factory() external view returns (address);
860
    function token0() external view returns (address);
861
    function token1() external view returns (address);
862
    function getReserves() external