// Contract: GlassDoor
// Target function: function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory)
// SPDX-License-Identifier: Unlicensed



pragma solidity ^0.6.12;



abstract contract Context {

    function _msgSender() internal view virtual returns (address payable) {

        return msg.sender;

    }



    function _msgData() internal view virtual returns (bytes memory) {

        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691

        return msg.data;

    }

}



interface IERC20 {

    /**

     * @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 `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);

}



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) {

        require(b > 0, errorMessage);

        uint256 c = a / b;

        // assert(a == b * c + a % b); // There is no case in which this doesn't hold



        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;

    }

}



library Address {

    /**

     * @dev Returns true if `account` is a contract.

     *

     * [IMPORTANT]

     * ====

     * It is unsafe to assume that an address for which this function returns

     * false is an externally-owned account (EOA) and not a contract.

     *

     * Among others, `isContract` will return false for the following

     * types of addresses:

     *

     *  - an externally-owned account

     *  - a contract in construction

     *  - an address where a contract will be created

     *  - an address where a contract lived, but was destroyed

     * ====

     */

    function isContract(address account) internal view returns (bool) {

        // According to EIP-1052, 0x0 is the value returned for not-yet created accounts

        // and 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470 is returned

        // for accounts without code, i.e. `keccak256('')`

        bytes32 codehash;

        bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;

        // solhint-disable-next-line no-inline-assembly

        assembly { codehash := extcodehash(account) }

        return (codehash != accountHash && codehash != 0x0);

    }



    /**

     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to

     * `recipient`, forwarding all available gas and reverting on errors.

     *

     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost

     * of certain opcodes, possibly making contracts go over the 2300 gas limit

     * imposed by `transfer`, making them unable to receive funds via

     * `transfer`. {sendValue} removes this limitation.

     *

     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].

     *

     * IMPORTANT: because control is transferred to `recipient`, care must be

     * taken to not create reentrancy vulnerabilities. Consider using

     * {ReentrancyGuard} or the

     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].

     */

    function sendValue(address payable recipient, uint256 amount) internal {

        require(address(this).balance >= amount, "Address: insufficient balance");



        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value

        (bool success, ) = recipient.call{ value: amount }("");

        require(success, "Address: unable to send value, recipient may have reverted");

    }



    /**

     * @dev Performs a Solidity function call using a low level `call`. A

     * plain`call` is an unsafe replacement for a function call: use this

     * function instead.

     *

     * If `target` reverts with a revert reason, it is bubbled up by this

     * function (like regular Solidity function calls).

     *

     * Returns the raw returned data. To convert to the expected return value,

     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].

     *

     * Requirements:

     *

     * - `target` must be a contract.

     * - calling `target` with `data` must not revert.

     *

     * _Available since v3.1._

     */

    function functionCall(address target, bytes memory data) internal returns (bytes memory) {

      return functionCall(target, data, "Address: low-level call failed");

    }



    /**

     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with

     * `errorMessage` as a fallback revert reason when `target` reverts.

     *

     * _Available since v3.1._

     */

    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {

        return _functionCallWithValue(target, data, 0, errorMessage);

    }



    /**

     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],

     * but also transferring `value` wei to `target`.

     *

     * Requirements:

     *

     * - the calling contract must have an ETH balance of at least `value`.

     * - the called Solidity function must be `payable`.

     *

     * _Available since v3.1._

     */

    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {

        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");

    }