using System;

​

class Stack

{

    int[] items = new int[100];

​

    public void Push(int item)

    {

    }

​

    public int Pop()

    {

        return -1;

    }

​

    public int Peek()

    {

        return -1;

    }

​

    public int Max()

    {

        return -1;

    }

​

}

​

public class Program

{

    public static void Main(string[] args)

    {

        Stack stack = new Stack();

        stack.Push(1); // 1

        stack.Push(5); // 1, 5

        stack.Push(8); // 1, 5, 8

        stack.Push(2); // 1, 5, 8, 2

        Debug.Assert(stack.Peek() == 2);

        Debug.Assert(stack.Max() == 8);

        stack.Pop(); // 1, 5, 8

        stack.Pop(); // 1, 5

        Debug.Assert(stack.Peek() == 5);

        Debug.Assert(stack.Max() == 5);

        stack.Push(9); // 1, 5, 9

        stack.Push(11); // 1, 5, 9, 11

        stack.Push(7); // 1, 5, 9, 11, 7

        Debug.Assert(stack.Peek() == 7);

        Debug.Assert(stack.Max() == 11);

        stack.Pop(); // 1, 5, 9, 11

        stack.Pop(); // 1, 5, 9

        stack.Pop(); // 1, 5

        Debug.Assert(stack.Peek() == 5);

        Debug.Assert(stack.Max() == 5);

        stack.Push(13); // 1, 5, 13

        stack.Push(13); // 1, 5, 13, 13

        stack.Push(10); // 1, 5, 13, 13, 10

        Debug.Assert(stack.Peek() == 10);

        Debug.Assert(stack.Max() == 13);

        stack.Push(15); // 1, 5, 13, 13, 10, 15

        stack.Push(15); // 1, 5, 13, 13, 10, 15, 15

        stack.Push(13); // 1, 5, 13, 13, 10, 15, 15, 13

        Debug.Assert(stack.Peek() == 13);

        Debug.Assert(stack.Max() == 15);

        stack.Pop(); // 1, 5, 13, 13, 10, 15, 15

        stack.Pop(); // 1, 5, 13, 13, 10, 15

        stack.Pop(); // 1, 5, 13, 13, 10

        Debug.Assert(stack.Peek() == 10);

        Debug.Assert(stack.Max() == 13);

        stack.Pop(); // 1, 5, 13, 13

        Debug.Assert(stack.Peek() == 13);

        Debug.Assert(stack.Max() == 13);

        stack.Pop(); // 1, 5, 13

        stack.Pop(); // 1, 5

        Debug.Assert(stack.Peek() == 5);

        Debug.Assert(stack.Max() == 5);

​

        Console.WriteLine("Done");

    }

​

}

​

public static class Debug

{

    public static void Assert(bool value)

    {

        if (!value)

        {

            throw new Exception("Assertion failed");

        }

        else

        {

            Console.WriteLine("Test passed");

        }

    }

}

​