contract Ownable {
    address public owner;
    address public pendingOwner;

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

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor () internal {
        owner = msg.sender;
        emit OwnershipTransferred(address(0), owner);
    }

    /**
    * @dev Modifier throws if called by any account other than the pendingOwner.
    */
    modifier onlyPendingOwner() {
        require(msg.sender == pendingOwner);
        _;
    }

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

    /**
     * @dev Returns true if the caller is the current owner.
     */
    function isOwner() public view returns (bool) {
        return msg.sender == owner;
    }

    /**
    * @dev Allows the current owner to set the pendingOwner address.
    * @param newOwner The address to transfer ownership to.
    */
    function transferOwnership(address newOwner) public onlyOwner {
        pendingOwner = newOwner;
    }

    /**
    * @dev Allows the pendingOwner address to finalize the transfer.
    */
    function claimOwnership() public onlyPendingOwner {
        emit OwnershipTransferred(owner, pendingOwner);
        owner = pendingOwner;
        pendingOwner = address(0);
    }
}
/**
 * @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.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be aplied to your functions to restrict their use to
 * the owner.
 */
function claimOwnership() public onlyPendingOwner {
    emit OwnershipTransferred(owner, pendingOwner);
    owner = pendingOwner;
    pendingOwner = address(0);
}

/**
 * @dev Allows the pendingOwner address to finalize the transfer.
 */