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 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;
      }
    
      /**
       * @dev Allows the current owner to relinquish control of the contract.
       */
      function renounceOwnership() public onlyOwner {
        emit OwnershipRenounced(owner);
        owner = address(0);
      }
    }
/**
 * @title Ownable
 * @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 onlyOwner {
  require(newOwner != address(0));
  emit OwnershipTransferred(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.
 */