using System;

public class Program

{

    public class Node

    {

        public int data;

        public Node next;

        public Node(int item)

        {

            data = item;

            next = null;

        }

    }

    public class Stackimpl

    {

        public bool IsEmpty(Node h)

        {

            if(h==null)

                return true;

            else 

                return false;

        }

        public Node Push(Node h, int item)

        {

            if(IsEmpty(h))

            {

                h = new Node(item);

                return h;

            }

            else

            {

                Node temp = new Node(item);

                temp.next = h;

                h= temp;

                return h;

            }

        }

        public Node Pop(Node h)

        {

            if(h==null)

            {

                Console.WriteLine("No data");

                return null;

            }

            else

            {

                Console.WriteLine(h.data);

                h = h.next;

                return h;

            }

        }

    }

    public static void Main()

    {

        Node head = null;

        Stackimpl stk = new Stackimpl();

        head = stk.Push(head, 1);

        head=stk.Push(head,2);

        Node currhead = stk.Pop(head);

        currhead = stk.Pop(currhead);

    }

}