Given the following partial code, fill in the blank to complete the code necessary to insert node x after the third node. $($don$\text{'}$t forget the semicolon$)$

$...$

class Node $\{$

public Object data $=$ null;

public Node next $=$ null;

$\}$

$...$

Node head $=$ new Node$()$; $//$ first Node

head.next $=$ new Node$()$; $//$ second Node

head.next.next $=$ new Node$()$; $//$ third node

Node x $=$ new Node$()$; $//$ node to insert

$\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_//$