contract Ownable {
  address public owner;
  event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
  /**
   * @dev The Ownable constructor sets the original `owner` of the contract to the sender
   * account.
   */
  /*@CTK owner_set_on_success
    @pre __reverted == false -> __post.owner == owner
   */
  /* CertiK Smart Labelling, for more details visit: https://certik.org */
  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.
   */
  /*@CTK transferOwnership
    @post __reverted == false -> (msg.sender == owner -> __post.owner == newOwner)
    @post (owner != msg.sender) -> (__reverted == true)
    @post (newOwner == address(0)) -> (__reverted == true)
   */
  /* CertiK Smart Labelling, for more details visit: https://certik.org */
  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 transferOwnership(address newOwner) public onlyOwner {
  require(newOwner != address(0));
  emit OwnershipTransferred(owner, newOwner);
  owner = newOwner;
}

/* CertiK Smart Labelling, for more details visit: https://certik.org */