using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace LinkedList
{
    class Program
    {
        static void Main(string[] args)
        {
            Stack stk = new Stack();

            stk.add(5);
            stk.add(4);
            stk.add(2);
            stk.add(7);

            while (!stk.empty())
            {
                Console.WriteLine(stk.top());
                stk.pop();
            }

            Console.WriteLine(stk.size());
        }
    }

    class Node
    {
        public int info;
        public Node next;

        public Node(int val)
        {
            info = val;
            next = null;
        }
    }

    class Stack
    {
        Node start = null;

        public void add(int val)
        {
            Node tmp = new Node(val);

            if (start == null)
            {
                start = tmp;
                return;
            }

            tmp.next = start;
            start = tmp;
        }

        public bool empty()
        {
            return (start == null);
        }

        public void pop()
        {
            if (start == null)
            {
                Console.WriteLine("Stack is empty!");
                return;
            }
            start = start.next;
        }

        public int top()
        {
            return start.info;
        }

        public int size()
        {
            int cnt = 0;
            Node q = start;
            while (q != null)
            {
                q = q.next;
                cnt++;
            }

            return cnt;
        }
    }

}