using System;

using System.Collections.Generic;                   

public class Program

{

    public static void Main()

    {

        Stack<int> a = new Stack<int>();

        a.Push(4);

        a.Push(7);

        a.Push(1);

        a.Push(7);

        foreach(var x in a)

        {

        Console.WriteLine(x);

        }

        Console.WriteLine("peek is ...." + a.Peek());

        Console.WriteLine("pop is ...." + a.Pop());

        foreach(var x in a)

        {

        Console.WriteLine(x);

        }

    }

}