contract Ownable
{
    address public owner;

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

    /// @dev The Ownable constructor sets the original `owner` of the contract
    ///      to the sender.
    constructor()
        public
    {
        owner = msg.sender;
    }

    /// @dev Throws if called by any account other than the owner.
    modifier onlyOwner()
    {
        require(msg.sender == owner, "UNAUTHORIZED");
        _;
    }

    /// @dev Allows the current owner to transfer control of the contract to a
    ///      new owner.
    /// @param newOwner The address to transfer ownership to.
    function transferOwnership(
        address newOwner
        )
        public
        virtual
        onlyOwner
    {
        require(newOwner != address(0), "ZERO_ADDRESS");
        emit OwnershipTransferred(owner, newOwner);
        owner = newOwner;
    }

    function renounceOwnership()
        public
        onlyOwner
    {
        emit OwnershipTransferred(owner, address(0));
        owner = address(0);
    }
}
/// @title Ownable
/// @author Brecht Devos - <brecht@loopring.org>
/// @dev The Ownable contract has an owner address, and provides basic
///      authorization control functions, this simplifies the implementation of
///      "user permissions".
function transferOwnership(
        address newOwner
        )
        public
        virtual
        onlyOwner
    {
        require(newOwner != address(0), "ZERO_ADDRESS");
        emit OwnershipTransferred(owner, newOwner);
        owner = newOwner;
    }
/// @dev Allows the current owner to transfer control of the contract to a
///      new owner.
/// @param newOwner The address to transfer ownership to.