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.
 * @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 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.
 * @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.
 */