contract Ownable {

    address internal _owner;

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

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

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

    /**
     * @dev Allows the current owner to relinquish control of the contract.
     * @notice Renouncing to ownership will leave the contract without an owner.
     * It will not be possible to call the functions with the `onlyOwner`
     * modifier anymore.
     */
    function renounceOwnership() public onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }

    /**
     * @dev Allows the current owner to transfer control of the contract to a newOwner.
     * @param newOwner The address to transfer ownership to.
     */
    function transferOwnership(address newOwner) public onlyOwner {
        require(newOwner != address(0));
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}
/**
 * @title Ownable
 * @dev The Ownable contract has an owner address, and provides basic authorization control
 * functions, this simplifies the implementation of "user permissions".
 */
function renounceOwnership() public onlyOwner {
    emit OwnershipTransferred(_owner, address(0));
    _owner = address(0);
}

/**
 * @dev Allows the current owner to relinquish control of the contract.
 * @notice Renouncing to ownership will leave the contract without an owner.
 * It will not be possible to call the functions with the `onlyOwner`
 * modifier anymore.
 */