// File: @openzeppelin/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (access/Ownable.sol)

pragma solidity ^0.8.0;

import "../utils/Context.sol";

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

// File: @openzeppelin/contracts/token/ERC20/ERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC20/ERC20.sol)

pragma solidity ^0.8.0;

import "./IERC20.sol";
import "./extensions/IERC20Metadata.sol";
import "../../utils/Context.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.zeppelin.solutions/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, _allowances[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 = _allowances[owner][spender];
        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
        unchecked {
            _approve(owner, spender, currentAllowance - subtractedValue);
        }

        return true;
    }

    /**
     * @dev Moves `amount` of tokens from `sender` to `recipient`.
     *
     * 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;
        }
        _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;
        _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;
        }
        _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 Spend `amount` form the allowance of `owner` toward `spender`.
     *
     * 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 {}
}

// File: @openzeppelin/contracts/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
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 `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);

    /**
     * @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);
}

// File: @openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/IERC20Metadata.sol)

pragma solidity ^0.8.0;

import "../IERC20.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/utils/SafeERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";
import "../../../utils/Address.sol";

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using Address for address;

    function safeTransfer(
        IERC20 token,
        address to,
        uint256 value
    ) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(
        IERC20 token,
        address from,
        address to,
        uint256 value
    ) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        require(
            (value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        uint256 newAllowance = token.allowance(address(this), spender) + value;
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        unchecked {
            uint256 oldAllowance = token.allowance(address(this), spender);
            require(oldAllowance >= value, "SafeERC20: decreased allowance below zero");
            uint256 newAllowance = oldAllowance - value;
            _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
        }
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) {
            // Return data is optional
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

// File: @openzeppelin/contracts/utils/Address.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (utils/Address.sol)

pragma solidity ^0.8.1;

/**
 * @dev Collection of functions related to the address type
 */
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
     * ====
     *
     * [IMPORTANT]
     * ====
     * You shouldn't rely on `isContract` to protect against flash loan attacks!
     *
     * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
     * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
     * constructor.
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize/address.code.length, which returns 0
        // for contracts in construction, since the code is only stored at the end
        // of the constructor execution.

        return account.code.length > 0;
    }

    /**
     * @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");

        (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");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");

        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        (bool success, bytes memory returndata) = target.staticcall(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verifies that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason using the provided one.
     *
     * _Available since v4.3._
     */
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: @openzeppelin/contracts/utils/Context.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

pragma solidity ^0.8.0;

/**
 * @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;
    }
}

// File: contracts/Vesting.sol



//SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import '@openzeppelin/contracts/token/ERC20/IERC20.sol';
import '@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol';
import '@openzeppelin/contracts/access/Ownable.sol';

import './interfaces/IVesting.sol';

import './utils/BokkyPooBahsDateTimeLibrary.sol';
import './utils/SafeERC20Holder.sol';
import './utils/Merkle.sol';

contract Vesting is IVesting, Ownable, SafeERC20Holder, Merkle {
    using SafeERC20 for IERC20;

    IERC20 public token;
    uint256 public startTimestamp;
    bytes32 public root;

    uint256 public fDay;
    uint256 public fMonth;
    uint256 public fYear;

    string[] public rounds = ['seed', 'strategic', 'private'];

    mapping(string => uint256) public quarters;
    mapping(address => uint256) public earned;

    constructor(address token_, address owner_) {
        token = IERC20(token_);

        fDay = 21;
        fMonth = 5;
        fYear = 2022;

        startTimestamp = BokkyPooBahsDateTimeLibrary.timestampFromDate(
            fYear,
            fMonth,
            fDay
        );

        quarters['seed'] = 4;
        quarters['strategic'] = 2;
        quarters['private'] = 2;

        transferOwnership(owner_);
    }

    /// @inheritdoc IVesting
    function claim(uint256[] memory allocations, bytes32[] memory proof) external {
        require(block.timestamp > startTimestamp, 'Vesting have not started');
        uint256 total = unclaimed(msg.sender, allocations, proof);
        require(
            token.balanceOf(address(this)) >= total,
            'Not enough tokens on Vesting contract'
        );
        earned[msg.sender] += total;
        require(total > 0, 'You cant claim more');
        token.safeTransfer(msg.sender, total);
        emit Claim(block.timestamp, msg.sender, total);
    }

    /// @inheritdoc IVesting
    function unclaimed(
        address user,
        uint256[] memory allocations,
        bytes32[] memory proof
    ) public view returns (uint256) {
        require(block.timestamp > startTimestamp, 'Vesting have not started');
        require(allocations.length == rounds.length, 'Wrong input');
        bytes32 leaf = toLeaf(allocations, user);

        require(verify(proof, root, leaf), 'Wrong proof');
        uint256 length = allocations.length;
        uint256 total;
        for (uint256 i = 0; i < length; i++) {
            string memory round = rounds[i];
            uint256 allocation = allocations[i];
            total += unclaimedPerRound(round, allocation);
        }

        return total - earned[user];
    }

    /// @inheritdoc IVesting
    function unclaimedPerRound(string memory round, uint256 allocation)
        public
        view
        returns (uint256)
    {
        uint256 quarters_ = quarters[round];

        uint256 day = BokkyPooBahsDateTimeLibrary.getDay(block.timestamp);
        uint256 month = BokkyPooBahsDateTimeLibrary.getMonth(block.timestamp);
        uint256 year = BokkyPooBahsDateTimeLibrary.getYear(block.timestamp);

        if (day < fDay) month--;

        uint256 monthsPast = (year - fYear) * 12 + month - fMonth;
        uint256 quartersPast = monthsPast / 4 + 1;

        uint256 result = (allocation * quartersPast) / quarters_;
        return result > allocation ? allocation : result;
    }

    function start() external onlyOwner {
        require(block.timestamp < startTimestamp, 'Vesting has been already started');

        startTimestamp = block.timestamp;
        fDay = BokkyPooBahsDateTimeLibrary.getDay(startTimestamp);
        fMonth = BokkyPooBahsDateTimeLibrary.getMonth(startTimestamp);
        fYear = BokkyPooBahsDateTimeLibrary.getYear(startTimestamp);

        emit Start(block.timestamp, msg.sender);
    }

    /// @inheritdoc IVesting
    function setRoot(bytes32 root_) external onlyOwner {
        root = root_;
        emit SetRoot(block.timestamp, msg.sender, root);
    }

    /// @inheritdoc IVesting
    function setQuarters(string memory round, uint256 newQuarters) external onlyOwner {
        quarters[round] = newQuarters;
        emit SetQuarters(block.timestamp, msg.sender, round, newQuarters);
    }

    /// @inheritdoc IVesting
    function setRounds(string[] memory rounds_) external onlyOwner {
        rounds = rounds_;
        emit SetRounds(block.timestamp, msg.sender, rounds_);
    }

    function withdraw(IERC20 token_, uint256 amount) external onlyOwner {
        _withdraw(token_, amount);
    }

    /// @dev calculate leaf from allocations and user
    /// @param allocations allocation of user
    /// @param user address of user
    function toLeaf(uint256[] memory allocations, address user)
        public
        pure
        returns (bytes32)
    {
        return keccak256(abi.encode(allocations, user));
    }
}

// File: contracts/interfaces/IVesting.sol



//SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

/**
 * @title IVesting
 * @author gotbit
 */

interface IVesting {
    event StartVesting(uint256 indexed timestamp, address indexed user);
    event SetRoot(uint256 indexed timestamp, address indexed user, bytes32 root);
    event SetQuarters(
        uint256 indexed timestamp,
        address indexed user,
        string round,
        uint256 newQuarters
    );
    event SetRounds(uint256 indexed timestamp, address indexed user, string[] rounds);
    event Claim(uint256 indexed timestamp, address indexed user, uint256 amount);
    event Start(uint256 indexed timestamp, address indexed user);

    /// @dev starts vesting
    function start() external;

    /// @dev sets root for round
    /// @param root Merke tree root
    function setRoot(bytes32 root) external;

    /// @dev sets quarters for round
    /// @param round name of round
    /// @param newQuarters new amount of quarters for round
    function setQuarters(string memory round, uint256 newQuarters) external;

    /// @dev sets parameters for round
    /// @param rounds names of rounds
    function setRounds(string[] memory rounds) external;

    /// @dev claims the reward
    /// @param allocations of tokens
    /// @param proof Merkle tree proof
    function claim(uint256[] memory allocations, bytes32[] memory proof) external;

    /// @dev total reward for user
    /// @param user address of user
    /// @param allocations of tokens
    /// @param proof Merkle tree proof
    /// @return unclaimed amount of tokens to claim
    function unclaimed(
        address user,
        uint256[] memory allocations,
        bytes32[] memory proof
    ) external view returns (uint256);

    /// @dev returns reward in round with allocation
    /// @param round name of round
    /// @param allocation alloction in round
    function unclaimedPerRound(string memory round, uint256 allocation)
        external
        view
        returns (uint256);
}

// File: contracts/utils/BokkyPooBahsDateTimeLibrary.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

// ----------------------------------------------------------------------------
// BokkyPooBah's DateTime Library v1.01
//
// A gas-efficient Solidity date and time library
//
// https://github.com/bokkypoobah/BokkyPooBahsDateTimeLibrary
//
// Tested date range 1970/01/01 to 2345/12/31
//
// Conventions:
// Unit      | Range         | Notes
// :-------- |:-------------:|:-----
// timestamp | >= 0          | Unix timestamp, number of seconds since 1970/01/01 00:00:00 UTC
// year      | 1970 ... 2345 |
// month     | 1 ... 12      |
// day       | 1 ... 31      |
// hour      | 0 ... 23      |
// minute    | 0 ... 59      |
// second    | 0 ... 59      |
// dayOfWeek | 1 ... 7       | 1 = Monday, ..., 7 = Sunday
//
//
// Enjoy. (c) BokkyPooBah / Bok Consulting Pty Ltd 2018-2019. The MIT Licence.
// ----------------------------------------------------------------------------

library BokkyPooBahsDateTimeLibrary {
    uint256 constant SECONDS_PER_DAY = 24 * 60 * 60;
    uint256 constant SECONDS_PER_HOUR = 60 * 60;
    uint256 constant SECONDS_PER_MINUTE = 60;
    int256 constant OFFSET19700101 = 2440588;

    uint256 constant DOW_MON = 1;
    uint256 constant DOW_TUE = 2;
    uint256 constant DOW_WED = 3;
    uint256 constant DOW_THU = 4;
    uint256 constant DOW_FRI = 5;
    uint256 constant DOW_SAT = 6;
    uint256 constant DOW_SUN = 7;

    // ------------------------------------------------------------------------
    // Calculate the number of days from 1970/01/01 to year/month/day using
    // the date conversion algorithm from
    //   http://aa.usno.navy.mil/faq/docs/JD_Formula.php
    // and subtracting the offset 2440588 so that 1970/01/01 is day 0
    //
    // days = day
    //      - 32075
    //      + 1461 * (year + 4800 + (month - 14) / 12) / 4
    //      + 367 * (month - 2 - (month - 14) / 12 * 12) / 12
    //      - 3 * ((year + 4900 + (month - 14) / 12) / 100) / 4
    //      - offset
    // ------------------------------------------------------------------------
    function _daysFromDate(
        uint256 year,
        uint256 month,
        uint256 day
    ) internal pure returns (uint256 _days) {
        require(year >= 1970);
        int256 _year = int256(year);
        int256 _month = int256(month);
        int256 _day = int256(day);

        int256 __days = _day -
            32075 +
            (1461 * (_year + 4800 + (_month - 14) / 12)) /
            4 +
            (367 * (_month - 2 - ((_month - 14) / 12) * 12)) /
            12 -
            (3 * ((_year + 4900 + (_month - 14) / 12) / 100)) /
            4 -
            OFFSET19700101;

        _days = uint256(__days);
    }

    // ------------------------------------------------------------------------
    // Calculate year/month/day from the number of days since 1970/01/01 using
    // the date conversion algorithm from
    //   http://aa.usno.navy.mil/faq/docs/JD_Formula.php
    // and adding the offset 2440588 so that 1970/01/01 is day 0
    //
    // int L = days + 68569 + offset
    // int N = 4 * L / 146097
    // L = L - (146097 * N + 3) / 4
    // year = 4000 * (L + 1) / 1461001
    // L = L - 1461 * year / 4 + 31
    // month = 80 * L / 2447
    // dd = L - 2447 * month / 80
    // L = month / 11
    // month = month + 2 - 12 * L
    // year = 100 * (N - 49) + year + L
    // ------------------------------------------------------------------------
    function _daysToDate(uint256 _days)
        internal
        pure
        returns (
            uint256 year,
            uint256 month,
            uint256 day
        )
    {
        int256 __days = int256(_days);

        int256 L = __days + 68569 + OFFSET19700101;
        int256 N = (4 * L) / 146097;
        L = L - (146097 * N + 3) / 4;
        int256 _year = (4000 * (L + 1)) / 1461001;
        L = L - (1461 * _year) / 4 + 31;
        int256 _month = (80 * L) / 2447;
        int256 _day = L - (2447 * _month) / 80;
        L = _month / 11;
        _month = _month + 2 - 12 * L;
        _year = 100 * (N - 49) + _year + L;

        year = uint256(_year);
        month = uint256(_month);
        day = uint256(_day);
    }

    function timestampFromDate(
        uint256 year,
        uint256 month,
        uint256 day
    ) internal pure returns (uint256 timestamp) {
        timestamp = _daysFromDate(year, month, day) * SECONDS_PER_DAY;
    }

    function timestampFromDateTime(
        uint256 year,
        uint256 month,
        uint256 day,
        uint256 hour,
        uint256 minute,
        uint256 second
    ) internal pure returns (uint256 timestamp) {
        timestamp =
            _daysFromDate(year, month, day) *
            SECONDS_PER_DAY +
            hour *
            SECONDS_PER_HOUR +
            minute *
            SECONDS_PER_MINUTE +
            second;
    }

    function timestampToDate(uint256 timestamp)
        internal
        pure
        returns (
            uint256 year,
            uint256 month,
            uint256 day
        )
    {
        (year, month, day) = _daysToDate(timestamp / SECONDS_PER_DAY);
    }

    function timestampToDateTime(uint256 timestamp)
        internal
        pure
        returns (
            uint256 year,
            uint256 month,
            uint256 day,
            uint256 hour,
            uint256 minute,
            uint256 second
        )
    {
        (year, month, day) = _daysToDate(timestamp / SECONDS_PER_DAY);
        uint256 secs = timestamp % SECONDS_PER_DAY;
        hour = secs / SECONDS_PER_HOUR;
        secs = secs % SECONDS_PER_HOUR;
        minute = secs / SECONDS_PER_MINUTE;
        second = secs % SECONDS_PER_MINUTE;
    }

    function isValidDate(
        uint256 year,
        uint256 month,
        uint256 day
    ) internal pure returns (bool valid) {
        if (year >= 1970 && month > 0 && month <= 12) {
            uint256 daysInMonth = _getDaysInMonth(year, month);
            if (day > 0 && day <= daysInMonth) {
                valid = true;
            }
        }
    }

    function isValidDateTime(
        uint256 year,
        uint256 month,
        uint256 day,
        uint256 hour,
        uint256 minute,
        uint256 second
    ) internal pure returns (bool valid) {
        if (isValidDate(year, month, day)) {
            if (hour < 24 && minute < 60 && second < 60) {
                valid = true;
            }
        }
    }

    function isLeapYear(uint256 timestamp) internal pure returns (bool leapYear) {
        (uint256 year, , ) = _daysToDate(timestamp / SECONDS_PER_DAY);
        leapYear = _isLeapYear(year);
    }

    function _isLeapYear(uint256 year) internal pure returns (bool leapYear) {
        leapYear = ((year % 4 == 0) && (year % 100 != 0)) || (year % 400 == 0);
    }

    function isWeekDay(uint256 timestamp) internal pure returns (bool weekDay) {
        weekDay = getDayOfWeek(timestamp) <= DOW_FRI;
    }

    function isWeekEnd(uint256 timestamp) internal pure returns (bool weekEnd) {
        weekEnd = getDayOfWeek(timestamp) >= DOW_SAT;
    }

    function getDaysInMonth(uint256 timestamp)
        internal
        pure
        returns (uint256 daysInMonth)
    {
        (uint256 year, uint256 month, ) = _daysToDate(timestamp / SECONDS_PER_DAY);
        daysInMonth = _getDaysInMonth(year, month);
    }

    function _getDaysInMonth(uint256 year, uint256 month)
        internal
        pure
        returns (uint256 daysInMonth)
    {
        if (
            month == 1 ||
            month == 3 ||
            month == 5 ||
            month == 7 ||
            month == 8 ||
            month == 10 ||
            month == 12
        ) {
            daysInMonth = 31;
        } else if (month != 2) {
            daysInMonth = 30;
        } else {
            daysInMonth = _isLeapYear(year) ? 29 : 28;
        }
    }

    // 1 = Monday, 7 = Sunday
    function getDayOfWeek(uint256 timestamp) internal pure returns (uint256 dayOfWeek) {
        uint256 _days = timestamp / SECONDS_PER_DAY;
        dayOfWeek = ((_days + 3) % 7) + 1;
    }

    function getYear(uint256 timestamp) internal pure returns (uint256 year) {
        (year, , ) = _daysToDate(timestamp / SECONDS_PER_DAY);
    }

    function getMonth(uint256 timestamp) internal pure returns (uint256 month) {
        (, month, ) = _daysToDate(timestamp / SECONDS_PER_DAY);
    }

    function getDay(uint256 timestamp) internal pure returns (uint256 day) {
        (, , day) = _daysToDate(timestamp / SECONDS_PER_DAY);
    }

    function getHour(uint256 timestamp) internal pure returns (uint256 hour) {
        uint256 secs = timestamp % SECONDS_PER_DAY;
        hour = secs / SECONDS_PER_HOUR;
    }

    function getMinute(uint256 timestamp) internal pure returns (uint256 minute) {
        uint256 secs = timestamp % SECONDS_PER_HOUR;
        minute = secs / SECONDS_PER_MINUTE;
    }

    function getSecond(uint256 timestamp) internal pure returns (uint256 second) {
        second = timestamp % SECONDS_PER_MINUTE;
    }

    function addYears(uint256 timestamp, uint256 _years)
        internal
        pure
        returns (uint256 newTimestamp)
    {
        (uint256 year, uint256 month, uint256 day) = _daysToDate(
            timestamp / SECONDS_PER_DAY
        );
        year += _years;
        uint256 daysInMonth = _getDaysInMonth(year, month);
        if (day > daysInMonth) {
            day = daysInMonth;
        }
        newTimestamp =
            _daysFromDate(year, month, day) *
            SECONDS_PER_DAY +
            (timestamp % SECONDS_PER_DAY);
        require(newTimestamp >= timestamp);
    }

    function addMonths(uint256 timestamp, uint256 _months)
        internal
        pure
        returns (uint256 newTimestamp)
    {
        (uint256 year, uint256 month, uint256 day) = _daysToDate(
            timestamp / SECONDS_PER_DAY
        );
        month += _months;
        year += (month - 1) / 12;
        month = ((month - 1) % 12) + 1;
        uint256 daysInMonth = _getDaysInMonth(year, month);
        if (day > daysInMonth) {
            day = daysInMonth;
        }
        newTimestamp =
            _daysFromDate(year, month, day) *
            SECONDS_PER_DAY +
            (timestamp % SECONDS_PER_DAY);
        require(newTimestamp >= timestamp);
    }

    function addDays(uint256 timestamp, uint256 _days)
        internal
        pure
        returns (uint256 newTimestamp)
    {
        newTimestamp = timestamp + _days * SECONDS_PER_DAY;
        require(newTimestamp >= timestamp);
    }

    function addHours(uint256 timestamp, uint256 _hours)
        internal
        pure
        returns (uint256 newTimestamp)
    {
        newTimestamp = timestamp + _hours * SECONDS_PER_HOUR;
        require(newTimestamp >= timestamp);
    }

    function addMinutes(uint256 timestamp, uint256 _minutes)
        internal
        pure
        returns (uint256 newTimestamp)
    {
        newTimestamp = timestamp + _minutes * SECONDS_PER_MINUTE;
        require(newTimestamp >= timestamp);
    }

    function addSeconds(uint256 timestamp, uint256 _seconds)
        internal
        pure
        returns (uint256 newTimestamp)
    {
        newTimestamp = timestamp + _seconds;
        require(newTimestamp >= timestamp);
    }

    function subYears(uint256 timestamp, uint256 _years)
        internal
        pure
        returns (uint256 newTimestamp)
    {
        (uint256 year, uint256 month, uint256 day) = _daysToDate(
            timestamp / SECONDS_PER_DAY
        );
        year -= _years;
        uint256 daysInMonth = _getDaysInMonth(year, month);
        if (day > daysInMonth) {
            day = daysInMonth;
        }
        newTimestamp =
            _daysFromDate(year, month, day) *
            SECONDS_PER_DAY +
            (timestamp % SECONDS_PER_DAY);
        require(newTimestamp <= timestamp);
    }

    function subMonths(uint256 timestamp, uint256 _months)
        internal
        pure
        returns (uint256 newTimestamp)
    {
        (uint256 year, uint256 month, uint256 day) = _daysToDate(
            timestamp / SECONDS_PER_DAY
        );
        uint256 yearMonth = year * 12 + (month - 1) - _months;
        year = yearMonth / 12;
        month = (yearMonth % 12) + 1;
        uint256 daysInMonth = _getDaysInMonth(year, month);
        if (day > daysInMonth) {
            day = daysInMonth;
        }
        newTimestamp =
            _daysFromDate(year, month, day) *
            SECONDS_PER_DAY +
            (timestamp % SECONDS_PER_DAY);
        require(newTimestamp <= timestamp);
    }

    function subDays(uint256 timestamp, uint256 _days)
        internal
        pure
        returns (uint256 newTimestamp)
    {
        newTimestamp = timestamp - _days * SECONDS_PER_DAY;
        require(newTimestamp <= timestamp);
    }

    function subHours(uint256 timestamp, uint256 _hours)
        internal
        pure
        returns (uint256 newTimestamp)
    {
        newTimestamp = timestamp - _hours * SECONDS_PER_HOUR;
        require(newTimestamp <= timestamp);
    }

    function subMinutes(uint256 timestamp, uint256 _minutes)
        internal
        pure
        returns (uint256 newTimestamp)
    {
        newTimestamp = timestamp - _minutes * SECONDS_PER_MINUTE;
        require(newTimestamp <= timestamp);
    }

    function subSeconds(uint256 timestamp, uint256 _seconds)
        internal
        pure
        returns (uint256 newTimestamp)
    {
        newTimestamp = timestamp - _seconds;
        require(newTimestamp <= timestamp);
    }

    function diffYears(uint256 fromTimestamp, uint256 toTimestamp)
        internal
        pure
        returns (uint256 _years)
    {
        require(fromTimestamp <= toTimestamp);
        (uint256 fromYear, , ) = _daysToDate(fromTimestamp / SECONDS_PER_DAY);
        (uint256 toYear, , ) = _daysToDate(toTimestamp / SECONDS_PER_DAY);
        _years = toYear - fromYear;
    }

    function diffMonths(uint256 fromTimestamp, uint256 toTimestamp)
        internal
        pure
        returns (uint256 _months)
    {
        require(fromTimestamp <= toTimestamp);
        (uint256 fromYear, uint256 fromMonth, ) = _daysToDate(
            fromTimestamp / SECONDS_PER_DAY
        );
        (uint256 toYear, uint256 toMonth, ) = _daysToDate(toTimestamp / SECONDS_PER_DAY);
        _months = toYear * 12 + toMonth - fromYear * 12 - fromMonth;
    }

    function diffDays(uint256 fromTimestamp, uint256 toTimestamp)
        internal
        pure
        returns (uint256 _days)
    {
        require(fromTimestamp <= toTimestamp);
        _days = (toTimestamp - fromTimestamp) / SECONDS_PER_DAY;
    }

    function diffHours(uint256 fromTimestamp, uint256 toTimestamp)
        internal
        pure
        returns (uint256 _hours)
    {
        require(fromTimestamp <= toTimestamp);
        _hours = (toTimestamp - fromTimestamp) / SECONDS_PER_HOUR;
    }

    function diffMinutes(uint256 fromTimestamp, uint256 toTimestamp)
        internal
        pure
        returns (uint256 _minutes)
    {
        require(fromTimestamp <= toTimestamp);
        _minutes = (toTimestamp - fromTimestamp) / SECONDS_PER_MINUTE;
    }

    function diffSeconds(uint256 fromTimestamp, uint256 toTimestamp)
        internal
        pure
        returns (uint256 _seconds)
    {
        require(fromTimestamp <= toTimestamp);
        _seconds = toTimestamp - fromTimestamp;
    }
}

// File: contracts/utils/Merkle.sol



//SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

/**
 * @title Merkle
 * @author gotbit
 */

contract Merkle {
    /// @dev verifies ogs
    /// @param proof array of bytes for merkle tree verifing
    /// @param root tree's root
    /// @param leaf keccak256 of user address
    function verify(
        bytes32[] memory proof,
        bytes32 root,
        bytes32 leaf
    ) public pure returns (bool) {
        bytes32 hash = leaf;
        for (uint256 i = 0; i < proof.length; i++) {
            bytes32 proofElement = proof[i];
            hash = hash < proofElement
                ? keccak256(abi.encode(hash, proofElement))
                : keccak256(abi.encode(proofElement, hash));
        }
        return hash == root;
    }
}

// File: contracts/utils/SafeERC20Holder.sol



//SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

/**
 * @title SafeTokenHolder
 * @author gotbit
 */

import '@openzeppelin/contracts/token/ERC20/ERC20.sol';
import '@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol';
import '@openzeppelin/contracts/access/Ownable.sol';

interface ISafeERC20Holder {
    event WithdrawToken(
        uint256 indexed timestamp,
        address indexed user,
        address token,
        uint256 amount
    );
}

contract SafeERC20Holder is ISafeERC20Holder {
    using SafeERC20 for IERC20;

    /// @dev withdraws specific `token_` from contract (if amount greater than balance withdraws all balance)
    /// @param token_ address of token
    /// @param amount uint id which be minted
    function _withdraw(IERC20 token_, uint256 amount) internal {
        if (token_.balanceOf(address(this)) < amount)
            amount = token_.balanceOf(address(this));
        token_.safeTransfer(msg.sender, amount);

        emit WithdrawToken(block.timestamp, msg.sender, address(token_), amount);
    }
}