/*
Twitter: https://twitter.com/vfscoin
Website: https://www.vintageflyingshrek.wtf
Telegram: https://t.me/vintageflyingshrek
*/

// SPDX-License-Identifier: MIT
pragma solidity 0.8.23;

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
  function _msgSender() internal view virtual returns (address) {
    return msg.sender;
  }

  function _msgData() internal view virtual returns (bytes calldata) {
    return msg.data;
  }
}

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
  /**
   * @dev Emitted when `value` tokens are moved from one account (`from`) to
   * another (`to`).
   *
   * Note that `value` may be zero.
   */
  event Transfer(address indexed from, address indexed to, uint256 value);

  /**
   * @dev Emitted when the allowance of a `spender` for an `owner` is set by
   * a call to {approve}. `value` is the new allowance.
   */
  event Approval(address indexed owner, address indexed spender, uint256 value);

  /**
   * @dev Returns the amount of tokens in existence.
   */
  function totalSupply() external view returns (uint256);

  /**
   * @dev Returns the amount of tokens owned by `account`.
   */
  function balanceOf(address account) external view returns (uint256);

  /**
   * @dev Moves `amount` tokens from the caller's account to `to`.
   *
   * Returns a boolean value indicating whether the operation succeeded.
   *
   * Emits a {Transfer} event.
   */
  function transfer(address to, uint256 amount) external returns (bool);

  /**
   * @dev Returns the remaining number of tokens that `spender` will be
   * allowed to spend on behalf of `owner` through {transferFrom}. This is
   * zero by default.
   *
   * This value changes when {approve} or {transferFrom} are called.
   */
  function allowance(
    address owner,
    address spender
  ) external view returns (uint256);

  /**
   * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
   *
   * Returns a boolean value indicating whether the operation succeeded.
   *
   * IMPORTANT: Beware that changing an allowance with this method brings the risk
   * that someone may use both the old and the new allowance by unfortunate
   * transaction ordering. One possible solution to mitigate this race
   * condition is to first reduce the spender's allowance to 0 and set the
   * desired value afterwards:
   * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
   *
   * Emits an {Approval} event.
   */
  function approve(address spender, uint256 amount) external returns (bool);

  /**
   * @dev Moves `amount` tokens from `from` to `to` using the
   * allowance mechanism. `amount` is then deducted from the caller's
   * allowance.
   *
   * Returns a boolean value indicating whether the operation succeeded.
   *
   * Emits a {Transfer} event.
   */
  function transferFrom(
    address from,
    address to,
    uint256 amount
  ) external returns (bool);
}

// File: @openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol

// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/IERC20Metadata.sol)

/**
 * @dev Interface for the optional metadata functions from the ERC20 standard.
 *
 * _Available since v4.1._
 */
interface IERC20Metadata is IERC20 {
  /**
   * @dev Returns the name of the token.
   */
  function name() external view returns (string memory);

  /**
   * @dev Returns the symbol of the token.
   */
  function symbol() external view returns (string memory);

  /**
   * @dev Returns the decimals places of the token.
   */
  function decimals() external view returns (uint8);
}

// File: @openzeppelin/contracts/token/ERC20/ERC20.sol

// OpenZeppelin Contracts (last updated v4.8.0) (token/ERC20/ERC20.sol)

/**
 * @dev Implementation of the {IERC20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism see {ERC20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.openzeppelin.com/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin Contracts guidelines: functions revert
 * instead returning `false` on failure. This behavior is nonetheless
 * conventional and does not conflict with the expectations of ERC20
 * applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20-approve}.
 */
contract ERC20 is Context, IERC20, IERC20Metadata {
  mapping(address => uint256) private _balances;

  mapping(address => mapping(address => uint256)) private _allowances;

  uint256 private _totalSupply;

  string private _name;
  string private _symbol;

  /**
   * @dev Sets the values for {name} and {symbol}.
   *
   * The default value of {decimals} is 18. To select a different value for
   * {decimals} you should overload it.
   *
   * All two of these values are immutable: they can only be set once during
   * construction.
   */
  constructor(string memory name_, string memory symbol_) {
    _name = name_;
    _symbol = symbol_;
  }

  /**
   * @dev Returns the name of the token.
   */
  function name() public view virtual override returns (string memory) {
    return _name;
  }

  /**
   * @dev Returns the symbol of the token, usually a shorter version of the
   * name.
   */
  function symbol() public view virtual override returns (string memory) {
    return _symbol;
  }

  /**
   * @dev Returns the number of decimals used to get its user representation.
   * For example, if `decimals` equals `2`, a balance of `505` tokens should
   * be displayed to a user as `5.05` (`505 / 10 ** 2`).
   *
   * Tokens usually opt for a value of 18, imitating the relationship between
   * Ether and Wei. This is the value {ERC20} uses, unless this function is
   * overridden;
   *
   * NOTE: This information is only used for _display_ purposes: it in
   * no way affects any of the arithmetic of the contract, including
   * {IERC20-balanceOf} and {IERC20-transfer}.
   */
  function decimals() public view virtual override returns (uint8) {
    return 18;
  }

  /**
   * @dev See {IERC20-totalSupply}.
   */
  function totalSupply() public view virtual override returns (uint256) {
    return _totalSupply;
  }

  /**
   * @dev See {IERC20-balanceOf}.
   */
  function balanceOf(
    address account
  ) public view virtual override returns (uint256) {
    return _balances[account];
  }

  /**
   * @dev See {IERC20-transfer}.
   *
   * Requirements:
   *
   * - `to` cannot be the zero address.
   * - the caller must have a balance of at least `amount`.
   */
  function transfer(
    address to,
    uint256 amount
  ) public virtual override returns (bool) {
    address owner = _msgSender();
    _transfer(owner, to, amount);
    return true;
  }

  /**
   * @dev See {IERC20-allowance}.
   */
  function allowance(
    address owner,
    address spender
  ) public view virtual override returns (uint256) {
    return _allowances[owner][spender];
  }

  /**
   * @dev See {IERC20-approve}.
   *
   * NOTE: If `amount` is the maximum `uint256`, the allowance is not updated on
   * `transferFrom`. This is semantically equivalent to an infinite approval.
   *
   * Requirements:
   *
   * - `spender` cannot be the zero address.
   */
  function approve(
    address spender,
    uint256 amount
  ) public virtual override returns (bool) {
    address owner = _msgSender();
    _approve(owner, spender, amount);
    return true;
  }

  /**
   * @dev See {IERC20-transferFrom}.
   *
   * Emits an {Approval} event indicating the updated allowance. This is not
   * required by the EIP. See the note at the beginning of {ERC20}.
   *
   * NOTE: Does not update the allowance if the current allowance
   * is the maximum `uint256`.
   *
   * Requirements:
   *
   * - `from` and `to` cannot be the zero address.
   * - `from` must have a balance of at least `amount`.
   * - the caller must have allowance for ``from``'s tokens of at least
   * `amount`.
   */
  function transferFrom(
    address from,
    address to,
    uint256 amount
  ) public virtual override returns (bool) {
    address spender = _msgSender();
    _spendAllowance(from, spender, amount);
    _transfer(from, to, amount);
    return true;
  }

  /**
   * @dev Atomically increases the allowance granted to `spender` by the caller.
   *
   * This is an alternative to {approve} that can be used as a mitigation for
   * problems described in {IERC20-approve}.
   *
   * Emits an {Approval} event indicating the updated allowance.
   *
   * Requirements:
   *
   * - `spender` cannot be the zero address.
   */
  function increaseAllowance(
    address spender,
    uint256 addedValue
  ) public virtual returns (bool) {
    address owner = _msgSender();
    _approve(owner, spender, allowance(owner, spender) + addedValue);
    return true;
  }

  /**
   * @dev Atomically decreases the allowance granted to `spender` by the caller.
   *
   * This is an alternative to {approve} that can be used as a mitigation for
   * problems described in {IERC20-approve}.
   *
   * Emits an {Approval} event indicating the updated allowance.
   *
   * Requirements:
   *
   * - `spender` cannot be the zero address.
   * - `spender` must have allowance for the caller of at least
   * `subtractedValue`.
   */
  function decreaseAllowance(
    address spender,
    uint256 subtractedValue
  ) public virtual returns (bool) {
    address owner = _msgSender();
    uint256 currentAllowance = allowance(owner, spender);
    require(
      currentAllowance >= subtractedValue,
      'ERC20: decreased allowance below zero'
    );
    unchecked {
      _approve(owner, spender, currentAllowance - subtractedValue);
    }

    return true;
  }

  /**
   * @dev Moves `amount` of tokens from `from` to `to`.
   *
   * This internal function is equivalent to {transfer}, and can be used to
   * e.g. implement automatic token fees, slashing mechanisms, etc.
   *
   * Emits a {Transfer} event.
   *
   * Requirements:
   *
   * - `from` cannot be the zero address.
   * - `to` cannot be the zero address.
   * - `from` must have a balance of at least `amount`.
   */
  function _transfer(
    address from,
    address to,
    uint256 amount
  ) internal virtual {
    require(from != address(0), 'ERC20: transfer from the zero address');
    require(to != address(0), 'ERC20: transfer to the zero address');

    _beforeTokenTransfer(from, to, amount);

    uint256 fromBalance = _balances[from];
    require(fromBalance >= amount, 'ERC20: transfer amount exceeds balance');
    unchecked {
      _balances[from] = fromBalance - amount;
      // Overflow not possible: the sum of all balances is capped by totalSupply, and the sum is preserved by
      // decrementing then incrementing.
      _balances[to] += amount;
    }

    emit Transfer(from, to, amount);

    _afterTokenTransfer(from, to, amount);
  }

  /** @dev Creates `amount` tokens and assigns them to `account`, increasing
   * the total supply.
   *
   * Emits a {Transfer} event with `from` set to the zero address.
   *
   * Requirements:
   *
   * - `account` cannot be the zero address.
   */
  function _mint(address account, uint256 amount) internal virtual {
    require(account != address(0), 'ERC20: mint to the zero address');

    _beforeTokenTransfer(address(0), account, amount);

    _totalSupply += amount;
    unchecked {
      // Overflow not possible: balance + amount is at most totalSupply + amount, which is checked above.
      _balances[account] += amount;
    }
    emit Transfer(address(0), account, amount);

    _afterTokenTransfer(address(0), account, amount);
  }

  /**
   * @dev Destroys `amount` tokens from `account`, reducing the
   * total supply.
   *
   * Emits a {Transfer} event with `to` set to the zero address.
   *
   * Requirements:
   *
   * - `account` cannot be the zero address.
   * - `account` must have at least `amount` tokens.
   */
  function _burn(address account, uint256 amount) internal virtual {
    require(account != address(0), 'ERC20: burn from the zero address');

    _beforeTokenTransfer(account, address(0), amount);

    uint256 accountBalance = _balances[account];
    require(accountBalance >= amount, 'ERC20: burn amount exceeds balance');
    unchecked {
      _balances[account] = accountBalance - amount;
      // Overflow not possible: amount <= accountBalance <= totalSupply.
      _totalSupply -= amount;
    }

    emit Transfer(account, address(0), amount);

    _afterTokenTransfer(account, address(0), amount);
  }

  /**
   * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
   *
   * This internal function is equivalent to `approve`, and can be used to
   * e.g. set automatic allowances for certain subsystems, etc.
   *
   * Emits an {Approval} event.
   *
   * Requirements:
   *
   * - `owner` cannot be the zero address.
   * - `spender` cannot be the zero address.
   */
  function _approve(
    address owner,
    address spender,
    uint256 amount
  ) internal virtual {
    require(owner != address(0), 'ERC20: approve from the zero address');
    require(spender != address(0), 'ERC20: approve to the zero address');

    _allowances[owner][spender] = amount;
    emit Approval(owner, spender, amount);
  }

  /**
   * @dev Updates `owner` s allowance for `spender` based on spent `amount`.
   *
   * Does not update the allowance amount in case of infinite allowance.
   * Revert if not enough allowance is available.
   *
   * Might emit an {Approval} event.
   */
  function _spendAllowance(
    address owner,
    address spender,
    uint256 amount
  ) internal virtual {
    uint256 currentAllowance = allowance(owner, spender);
    if (currentAllowance != type(uint256).max) {
      require(currentAllowance >= amount, 'ERC20: insufficient allowance');
      unchecked {
        _approve(owner, spender, currentAllowance - amount);
      }
    }
  }

  /**
   * @dev Hook that is called before any transfer of tokens. This includes
   * minting and burning.
   *
   * Calling conditions:
   *
   * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
   * will be transferred to `to`.
   * - when `from` is zero, `amount` tokens will be minted for `to`.
   * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
   * - `from` and `to` are never both zero.
   *
   * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
   */
  function _beforeTokenTransfer(
    address from,
    address to,
    uint256 amount
  ) internal virtual {}

  /**
   * @dev Hook that is called after any transfer of tokens. This includes
   * minting and burning.
   *
   * Calling conditions:
   *
   * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
   * has been transferred to `to`.
   * - when `from` is zero, `amount` tokens have been minted for `to`.
   * - when `to` is zero, `amount` of ``from``'s tokens have been burned.
   * - `from` and `to` are never both zero.
   *
   * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
   */
  function _afterTokenTransfer(
    address from,
    address to,
    uint256 amount
  ) internal virtual {}
}

abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    constructor() {
        _transferOwnership(_msgSender());
    }

    function owner() public view virtual returns (address) {
        return _owner;
    }

    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _transferOwnership(newOwner);
    }

    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

interface IUniswapV2Factory {
  function createPair(
    address tokenA,
    address tokenB
  ) external returns (address pair);
}

interface IUniswapV2Router02 {
  function factory() external pure returns (address);

  function WETH() external pure returns (address);

  function swapExactTokensForETHSupportingFeeOnTransferTokens(
    uint amountIn,
    uint amountOutMin,
    address[] calldata path,
    address to,
    uint deadline
  ) external;
}

library Math {
  /**
   * @dev Muldiv operation overflow.
   */
  error MathOverflowedMulDiv();

  enum Rounding {
    Floor, // Toward negative infinity
    Ceil, // Toward positive infinity
    Trunc, // Toward zero
    Expand // Away from zero
  }

  /**
   * @dev Returns the addition of two unsigned integers, with an overflow flag.
   */
  function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
    unchecked {
      uint256 c = a + b;
      if (c < a) return (false, 0);
      return (true, c);
    }
  }

  /**
   * @dev Returns the subtraction of two unsigned integers, with an overflow flag.
   */
  function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
    unchecked {
      if (b > a) return (false, 0);
      return (true, a - b);
    }
  }

  /**
   * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
   */
  function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
    unchecked {
      // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
      // benefit is lost if 'b' is also tested.
      // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
      if (a == 0) return (true, 0);
      uint256 c = a * b;
      if (c / a != b) return (false, 0);
      return (true, c);
    }
  }

  /**
   * @dev Returns the division of two unsigned integers, with a division by zero flag.
   */
  function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
    unchecked {
      if (b == 0) return (false, 0);
      return (true, a / b);
    }
  }

  /**
   * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
   */
  function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
    unchecked {
      if (b == 0) return (false, 0);
      return (true, a % b);
    }
  }

  /**
   * @dev Returns the largest of two numbers.
   */
  function max(uint256 a, uint256 b) internal pure returns (uint256) {
    return a > b ? a : b;
  }

  /**
   * @dev Returns the smallest of two numbers.
   */
  function min(uint256 a, uint256 b) internal pure returns (uint256) {
    return a < b ? a : b;
  }

  /**
   * @dev Returns the average of two numbers. The result is rounded towards
   * zero.
   */
  function average(uint256 a, uint256 b) internal pure returns (uint256) {
    // (a + b) / 2 can overflow.
    return (a & b) + (a ^ b) / 2;
  }

  /**
   * @dev Returns the ceiling of the division of two numbers.
   *
   * This differs from standard division with `/` in that it rounds towards infinity instead
   * of rounding towards zero.
   */
  function ceilDiv(uint256 a, uint256 b) internal pure returns (uint256) {
    if (b == 0) {
      // Guarantee the same behavior as in a regular Solidity division.
      return a / b;
    }

    // (a + b - 1) / b can overflow on addition, so we distribute.
    return a == 0 ? 0 : (a - 1) / b + 1;
  }

  /**
   * @notice Calculates floor(x * y / denominator) with full precision. Throws if result overflows a uint256 or denominator == 0
   * @dev Original credit to Remco Bloemen under MIT license (https://xn--2-umb.com/21/muldiv)
   * with further edits by Uniswap Labs also under MIT license.
   */
  function mulDiv(
    uint256 x,
    uint256 y,
    uint256 denominator
  ) internal pure returns (uint256 result) {
    unchecked {
      // 512-bit multiply [prod1 prod0] = x * y. Compute the product mod 2^256 and mod 2^256 - 1, then use
      // use the Chinese Remainder Theorem to reconstruct the 512 bit result. The result is stored in two 256
      // variables such that product = prod1 * 2^256 + prod0.
      uint256 prod0; // Least significant 256 bits of the product
      uint256 prod1; // Most significant 256 bits of the product
      assembly {
        let mm := mulmod(x, y, not(0))
        prod0 := mul(x, y)
        prod1 := sub(sub(mm, prod0), lt(mm, prod0))
      }

      // Handle non-overflow cases, 256 by 256 division.
      if (prod1 == 0) {
        // Solidity will revert if denominator == 0, unlike the div opcode on its own.
        // The surrounding unchecked block does not change this fact.
        // See https://docs.soliditylang.org/en/latest/control-structures.html#checked-or-unchecked-arithmetic.
        return prod0 / denominator;
      }

      // Make sure the result is less than 2^256. Also prevents denominator == 0.
      if (denominator <= prod1) {
        revert MathOverflowedMulDiv();
      }

      ///////////////////////////////////////////////
      // 512 by 256 division.
      ///////////////////////////////////////////////

      // Make division exact by subtracting the remainder from [prod1 prod0].
      uint256 remainder;
      assembly {
        // Compute remainder using mulmod.
        remainder := mulmod(x, y, denominator)

        // Subtract 256 bit number from 512 bit number.
        prod1 := sub(prod1, gt(remainder, prod0))
        prod0 := sub(prod0, remainder)
      }

      // Factor powers of two out of denominator and compute largest power of two divisor of denominator. Always >= 1.
      // See https://cs.stackexchange.com/q/138556/92363.

      // Does not overflow because the denominator cannot be zero at this stage in the function.
      uint256 twos = denominator & (~denominator + 1);
      assembly {
        // Divide denominator by twos.
        denominator := div(denominator, twos)

        // Divide [prod1 prod0] by twos.
        prod0 := div(prod0, twos)

        // Flip twos such that it is 2^256 / twos. If twos is zero, then it becomes one.
        twos := add(div(sub(0, twos), twos), 1)
      }

      // Shift in bits from prod1 into prod0.
      prod0 |= prod1 * twos;

      // Invert denominator mod 2^256. Now that denominator is an odd number, it has an inverse modulo 2^256 such
      // that denominator * inv = 1 mod 2^256. Compute the inverse by starting with a seed that is correct for
      // four bits. That is, denominator * inv = 1 mod 2^4.
      uint256 inverse = (3 * denominator) ^ 2;

      // Use the Newton-Raphson iteration to improve the precision. Thanks to Hensel's lifting lemma, this also works
      // in modular arithmetic, doubling the correct bits in each step.
      inverse *= 2 - denominator * inverse; // inverse mod 2^8
      inverse *= 2 - denominator * inverse; // inverse mod 2^16
      inverse *= 2 - denominator * inverse; // inverse mod 2^32
      inverse *= 2 - denominator * inverse; // inverse mod 2^64
      inverse *= 2 - denominator * inverse; // inverse mod 2^128
      inverse *= 2 - denominator * inverse; // inverse mod 2^256

      // Because the division is now exact we can divide by multiplying with the modular inverse of denominator.
      // This will give us the correct result modulo 2^256. Since the preconditions guarantee that the outcome is
      // less than 2^256, this is the final result. We don't need to compute the high bits of the result and prod1
      // is no longer required.
      result = prod0 * inverse;
      return result;
    }
  }

  /**
   * @notice Calculates x * y / denominator with full precision, following the selected rounding direction.
   */
  function mulDiv(
    uint256 x,
    uint256 y,
    uint256 denominator,
    Rounding rounding
  ) internal pure returns (uint256) {
    uint256 result = mulDiv(x, y, denominator);
    if (unsignedRoundsUp(rounding) && mulmod(x, y, denominator) > 0) {
      result += 1;
    }
    return result;
  }

  /**
   * @dev Returns the square root of a number. If the number is not a perfect square, the value is rounded
   * towards zero.
   *
   * Inspired by Henry S. Warren, Jr.'s "Hacker's Delight" (Chapter 11).
   */
  function sqrt(uint256 a) internal pure returns (uint256) {
    if (a == 0) {
      return 0;
    }

    // For our first guess, we get the biggest power of 2 which is smaller than the square root of the target.
    //
    // We know that the "msb" (most significant bit) of our target number `a` is a power of 2 such that we have
    // `msb(a) <= a < 2*msb(a)`. This value can be written `msb(a)=2**k` with `k=log2(a)`.
    //
    // This can be rewritten `2**log2(a) <= a < 2**(log2(a) + 1)`
    // → `sqrt(2**k) <= sqrt(a) < sqrt(2**(k+1))`
    // → `2**(k/2) <= sqrt(a) < 2**((k+1)/2) <= 2**(k/2 + 1)`
    //
    // Consequently, `2**(log2(a) / 2)` is a good first approximation of `sqrt(a)` with at least 1 correct bit.
    uint256 result = 1 << (log2(a) >> 1);

    // At this point `result` is an estimation with one bit of precision. We know the true value is a uint128,
    // since it is the square root of a uint256. Newton's method converges quadratically (precision doubles at
    // every iteration). We thus need at most 7 iteration to turn our partial result with one bit of precision
    // into the expected uint128 result.
    unchecked {
      result = (result + a / result) >> 1;
      result = (result + a / result) >> 1;
      result = (result + a / result) >> 1;
      result = (result + a / result) >> 1;
      result = (result + a / result) >> 1;
      result = (result + a / result) >> 1;
      result = (result + a / result) >> 1;
      return min(result, a / result);
    }
  }

  /**
   * @notice Calculates sqrt(a), following the selected rounding direction.
   */
  function sqrt(uint256 a, Rounding rounding) internal pure returns (uint256) {
    unchecked {
      uint256 result = sqrt(a);
      return
        result + (unsignedRoundsUp(rounding) && result * result < a ? 1 : 0);
    }
  }

  /**
   * @dev Return the log in base 2 of a positive value rounded towards zero.
   * Returns 0 if given 0.
   */
  function log2(uint256 value) internal pure returns (uint256) {
    uint256 result = 0;
    unchecked {
      if (value >> 128 > 0) {
        value >>= 128;
        result += 128;
      }
      if (value >> 64 > 0) {
        value >>= 64;
        result += 64;
      }
      if (value >> 32 > 0) {
        value >>= 32;
        result += 32;
      }
      if (value >> 16 > 0) {
        value >>= 16;
        result += 16;
      }
      if (value >> 8 > 0) {
        value >>= 8;
        result += 8;
      }
      if (value >> 4 > 0) {
        value >>= 4;
        result += 4;
      }
      if (value >> 2 > 0) {
        value >>= 2;
        result += 2;
      }
      if (value >> 1 > 0) {
        result += 1;
      }
    }
    return result;
  }

  /**
   * @dev Return the log in base 2, following the selected rounding direction, of a positive value.
   * Returns 0 if given 0.
   */
  function log2(
    uint256 value,
    Rounding rounding
  ) internal pure returns (uint256) {
    unchecked {
      uint256 result = log2(value);
      return
        result + (unsignedRoundsUp(rounding) && 1 << result < value ? 1 : 0);
    }
  }

  /**
   * @dev Return the log in base 10 of a positive value rounded towards zero.
   * Returns 0 if given 0.
   */
  function log10(uint256 value) internal pure returns (uint256) {
    uint256 result = 0;
    unchecked {
      if (value >= 10 ** 64) {
        value /= 10 ** 64;
        result += 64;
      }
      if (value >= 10 ** 32) {
        value /= 10 ** 32;
        result += 32;
      }
      if (value >= 10 ** 16) {
        value /= 10 ** 16;
        result += 16;
      }
      if (value >= 10 ** 8) {
        value /= 10 ** 8;
        result += 8;
      }
      if (value >= 10 ** 4) {
        value /= 10 ** 4;
        result += 4;
      }
      if (value >= 10 ** 2) {
        value /= 10 ** 2;
        result += 2;
      }
      if (value >= 10 ** 1) {
        result += 1;
      }
    }
    return result;
  }

  /**
   * @dev Return the log in base 10, following the selected rounding direction, of a positive value.
   * Returns 0 if given 0.
   */
  function log10(
    uint256 value,
    Rounding rounding
  ) internal pure returns (uint256) {
    unchecked {
      uint256 result = log10(value);
      return
        result + (unsignedRoundsUp(rounding) && 10 ** result < value ? 1 : 0);
    }
  }

  /**
   * @dev Return the log in base 256 of a positive value rounded towards zero.
   * Returns 0 if given 0.
   *
   * Adding one to the result gives the number of pairs of hex symbols needed to represent `value` as a hex string.
   */
  function log256(uint256 value) internal pure returns (uint256) {
    uint256 result = 0;
    unchecked {
      if (value >> 128 > 0) {
        value >>= 128;
        result += 16;
      }
      if (value >> 64 > 0) {
        value >>= 64;
        result += 8;
      }
      if (value >> 32 > 0) {
        value >>= 32;
        result += 4;
      }
      if (value >> 16 > 0) {
        value >>= 16;
        result += 2;
      }
      if (value >> 8 > 0) {
        result += 1;
      }
    }
    return result;
  }

  /**
   * @dev Return the log in base 256, following the selected rounding direction, of a positive value.
   * Returns 0 if given 0.
   */
  function log256(
    uint256 value,
    Rounding rounding
  ) internal pure returns (uint256) {
    unchecked {
      uint256 result = log256(value);
      return
        result +
        (unsignedRoundsUp(rounding) && 1 << (result << 3) < value ? 1 : 0);
    }
  }

  /**
   * @dev Returns whether a provided rounding mode is considered rounding up for unsigned integers.
   */
  function unsignedRoundsUp(Rounding rounding) internal pure returns (bool) {
    return uint8(rounding) % 2 == 1;
  }
}

abstract contract ReentrancyGuard {
  // Booleans are more expensive than uint256 or any type that takes up a full
  // word because each write operation emits an extra SLOAD to first read the
  // slot's contents, replace the bits taken up by the boolean, and then write
  // back. This is the compiler's defense against contract upgrades and
  // pointer aliasing, and it cannot be disabled.

  // The values being non-zero value makes deployment a bit more expensive,
  // but in exchange the refund on every call to nonReentrant will be lower in
  // amount. Since refunds are capped to a percentage of the total
  // transaction's gas, it is best to keep them low in cases like this one, to
  // increase the likelihood of the full refund coming into effect.
  uint256 private constant _NOT_ENTERED = 1;
  uint256 private constant _ENTERED = 2;

  uint256 private _status;

  /**
   * @dev Unauthorized reentrant call.
   */
  error ReentrancyGuardReentrantCall();

  constructor() {
    _status = _NOT_ENTERED;
  }

  /**
   * @dev Prevents a contract from calling itself, directly or indirectly.
   * Calling a `nonReentrant` function from another `nonReentrant`
   * function is not supported. It is possible to prevent this from happening
   * by making the `nonReentrant` function external, and making it call a
   * `private` function that does the actual work.
   */
  modifier nonReentrant() {
    _nonReentrantBefore();
    _;
    _nonReentrantAfter();
  }

  function _nonReentrantBefore() private {
    // On the first call to nonReentrant, _status will be _NOT_ENTERED
    if (_status == _ENTERED) {
      revert ReentrancyGuardReentrantCall();
    }

    // Any calls to nonReentrant after this point will fail
    _status = _ENTERED;
  }

  function _nonReentrantAfter() private {
    // By storing the original value once again, a refund is triggered (see
    // https://eips.ethereum.org/EIPS/eip-2200)
    _status = _NOT_ENTERED;
  }

  /**
   * @dev Returns true if the reentrancy guard is currently set to "entered", which indicates there is a
   * `nonReentrant` function in the call stack.
   */
  function _reentrancyGuardEntered() internal view returns (bool) {
    return _status == _ENTERED;
  }
}

contract VintageFlyingShrek is Ownable, ERC20, ReentrancyGuard {
  error TradingClosed();
  error TransactionTooLarge();
  error MaxBalanceExceeded();
  error PercentOutOfRange();
  error NotExternalToken();
  error TransferFailed();

  bool public tradingOpen;
  bool private _inSwap;

  address public marketingFeeReceiver;
  uint256 public maxTxAmount;
  uint256 public maxWalletBalance;
  mapping(address => bool) public _authorizations;
  mapping(address => bool) public _isExcludedFromFees;

  address public constant _ROUTER = 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D;
  address public immutable uniswapV2Pair;

  uint256 public swapThreshold;
  uint256 public sellTax;
  uint256 public buyTax;

  modifier swapping() {
    _inSwap = true;
    _;
    _inSwap = false;
  }


  constructor(
  ) ERC20("Vintage Flying Shrek", "VFS") {
    uint256 supply = 1000000000 * 1 ether;

    swapThreshold = Math.mulDiv(supply, 6, 1000);
    marketingFeeReceiver = msg.sender;
    buyTax = 0;
    sellTax = 0;

    maxWalletBalance = Math.mulDiv(supply, 15, 1000);
    maxTxAmount = Math.mulDiv(supply, 15, 1000);

    IUniswapV2Router02 router = IUniswapV2Router02(_ROUTER);
    address pair = IUniswapV2Factory(router.factory()).createPair(
      router.WETH(),
      address(this)
    );
    uniswapV2Pair = pair;
    
    _authorizations[msg.sender] = true;
    _authorizations[address(this)] = true;
    _authorizations[address(0xdead)] = true;
    _authorizations[address(0)] = true;
    _authorizations[pair] = true;
    _authorizations[address(router)] = true;

    _isExcludedFromFees[msg.sender] = true;
    _isExcludedFromFees[address(this)] = true;

    _approve(msg.sender, _ROUTER, type(uint256).max);
    _approve(msg.sender, pair, type(uint256).max);
    _approve(address(this), _ROUTER, type(uint256).max);
    _approve(address(this), pair, type(uint256).max);

    _mint(msg.sender, supply);
  }

  function setMaxWalletAndTxPercent(
    uint256 _maxWalletPercent,
    uint256 _maxTxPercent
  ) external onlyOwner {
    if (_maxWalletPercent == 0 || _maxWalletPercent > 100) {
      revert PercentOutOfRange();
    }
    if (_maxTxPercent == 0 || _maxTxPercent > 100) {
      revert PercentOutOfRange();
    }
    uint256 supply = totalSupply();

    maxWalletBalance = Math.mulDiv(supply, _maxWalletPercent, 100);
    maxTxAmount = Math.mulDiv(supply, _maxTxPercent, 100);
  }

  function setExemptFromMaxTx(address addr, bool value) public onlyOwner {
    _authorizations[addr] = value;
  }

  function setExemptFromFee(address addr, bool value) public onlyOwner {
    _isExcludedFromFees[addr] = value;
  }

  function _transfer(
    address _from,
    address _to,
    uint256 _amount
  ) internal override {
    if (_shouldSwapBack()) {
      _swapBack();
    }
    if (_inSwap) {
      return super._transfer(_from, _to, _amount);
    }

    uint256 fee = (_isExcludedFromFees[_from] || _isExcludedFromFees[_to])
      ? 0
      : _calculateFee(_from, _to, _amount);

    if (fee != 0) {
      super._transfer(_from, address(this), fee);
      _amount -= fee;
    }

    super._transfer(_from, _to, _amount);
  }

  function _swapBack() internal swapping nonReentrant {
    IUniswapV2Router02 router = IUniswapV2Router02(_ROUTER);
    address[] memory path = new address[](2);
    path[0] = address(this);
    path[1] = router.WETH();

    router.swapExactTokensForETHSupportingFeeOnTransferTokens(
      swapThreshold,
      0,
      path,
      address(this),
      block.timestamp
    );

    uint256 balance = address(this).balance;

    (bool success, ) = payable(marketingFeeReceiver).call{value: balance}('');
    if (!success) {
      revert TransferFailed();
    }
  }

  function _calculateFee(
    address sender,
    address recipient,
    uint256 amount
  ) internal view returns (uint256) {
    if (recipient == uniswapV2Pair) {
      return Math.mulDiv(amount, sellTax, 100);
    } else if (sender == uniswapV2Pair) {
      return Math.mulDiv(amount, buyTax, 100);
    }

    return (0);
  }

  function _shouldSwapBack() internal view returns (bool) {
    return
      msg.sender != uniswapV2Pair &&
      !_inSwap &&
      balanceOf(address(this)) >= swapThreshold;
  }

  function clearStuckToken(
    address tokenAddress,
    uint256 tokens
  ) external returns (bool success) {
    if (tokenAddress == address(this)) {
      revert NotExternalToken();
    } else {
      if (tokens == 0) {
        tokens = ERC20(tokenAddress).balanceOf(address(this));
        return ERC20(tokenAddress).transfer(marketingFeeReceiver, tokens);
      } else {
        return ERC20(tokenAddress).transfer(marketingFeeReceiver, tokens);
      }
    }
  }

  function setTaxes(uint256 _buyTax, uint256 _sellTax) external onlyOwner {
    sellTax = _sellTax;
    buyTax = _buyTax;
  }

  function openTrading() public onlyOwner {
    tradingOpen = true;
  }

  function setMarketingWallet(
    address _marketingFeeReceiver
  ) external onlyOwner {
    marketingFeeReceiver = _marketingFeeReceiver;
  }

  function setSwapBackSettings(uint256 _amount) public onlyOwner{
    uint256 total = totalSupply();
    uint newAmount = _amount * 1 ether;
    require(
      newAmount >= total / 1000 && newAmount <= total / 20,
      'The amount should be between 0.1% and 5% of total supply'
    );
    swapThreshold = newAmount;
  }

  function isAuthorized(address addr) public view returns (bool) {
    return _authorizations[addr];
  }

  function _beforeTokenTransfer(
    address _from,
    address _to,
    uint256 _amount
  ) internal view override {
    if (!tradingOpen) {
      if (!_authorizations[_from] || !_authorizations[_to]) {
        revert TradingClosed();
      }
    }
    if (!_authorizations[_to]) {
      if ((balanceOf(_to) + _amount) > maxWalletBalance) {
        revert MaxBalanceExceeded();
      }
    }
    if (!_authorizations[_from]) {
      if (_amount > maxTxAmount) {
        revert TransactionTooLarge();
      }
    }
  }

  receive() external payable {}

  fallback() external payable {}
}