contract Ownable {
  address public owner;
  address public pendingOwner;

  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 Throws if called by any account other than the pendingOwner.
   */
  modifier onlyPendingOwner() {
    assert(msg.sender != address(0));
    require(msg.sender == pendingOwner);
    _;
  }


  /**
   * @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) onlyOwner public {
    require(newOwner != address(0));
    pendingOwner = newOwner;
  }
  
  /**
   * @dev Allows the pendingOwner address to finalize the transfer.
   */
  function claimOwnership() onlyPendingOwner public {
    emit OwnershipTransferred(owner, pendingOwner);
    owner = pendingOwner;
    pendingOwner = 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 claimOwnership() onlyPendingOwner public {
  emit OwnershipTransferred(owner, pendingOwner);
  owner = pendingOwner;
  pendingOwner = address(0);
}

/**
 * @dev Allows the pendingOwner address to finalize the transfer.
 */