using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        Node root = new Node(10);

        root.leftNode = new Node(20);

        root.leftNode.leftNode = new Node(40);

        root.leftNode.rightNode = new Node(50);

        root.rightNode = new Node(30);

        root.rightNode.rightNode = new Node(70);

        printNodesAtK(root, 2);

    }

    public static void printNodesAtK(Node root, int k)

    {

        if(root == null){return;}

        if(k == 0){Console.WriteLine(root.value);}

        else

        {

            printNodesAtK(root.leftNode, k-1);

            printNodesAtK(root.rightNode, k-1);

        }

    }

}

​

public class Node

{

    public int value;

    public Node leftNode;

    public Node rightNode;

    public Node(int k)

    {

        value = k;

    }

}

​

​

​