contract Ownable {
address public owner;


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


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

/**
* @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.
*/
function renounceOwnership() public onlyOwner {
emit OwnershipRenounced(owner);
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 {
_transferOwnership(_newOwner);
}

/**
* @dev Transfers control of the contract to a newOwner.
* @param _newOwner The address to transfer ownership to.
*/
function _transferOwnership(address _newOwner) internal {
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 OwnershipRenounced(owner);
owner = address(0);
}
/**
 * @dev Allows the current owner to relinquish control of the contract.
 */