using System;

using System.Collections;

​

public class Program

{

    public static void Main()

    {

        Stack s = new Stack();

        s.Push(20);

        s.Push("aaa");

        s.Push(10);

        s.Push("bb");

        foreach (object ob in s)

        {

            Console.WriteLine(ob);

        }

        Console.WriteLine();

        Console.WriteLine(s.Contains(10));

        object s2=s.Clone();

        Console.WriteLine(s2);

    }

}