contract Ownable {
    address public owner;

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

    /**
     * @dev The Ownable constructor sets the original `owner` of the contract to the sender
     * account.
     */
    function Ownable() public {
    }

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

    /**
     * @dev Allows the current owner to transfer control of the contract to a newOwner.
     * @param _newOwner The address to transfer ownership to.
     */
    function changeOwner(address _newOwner) onlyOwner public {
        require(_newOwner != address(0));
        OwnerChanged(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 changeOwner(address _newOwner) onlyOwner public {
    require(_newOwner != address(0));
    OwnerChanged(owner, _newOwner);
    owner = _newOwner;
}

/**
 * @dev Allows the current owner to transfer control of the contract to a newOwner.
 * @param _newOwner The address to transfer ownership to.
 */