​

using System;

public class Program

{

    public class TreeNode {

    public int val;

    public TreeNode left;

    public TreeNode right;

    public TreeNode(int x) { val = x; }

    }

public static int MaxDepth(TreeNode root) {

    int maxD = 0;

    TreeNode current = root;

    while(current!=null)

    {

    }

    }

    public static void Main()

    {

        Console.WriteLine("Hello World");

    }

}