AiSD1_1

using System;

namespace AiSD1
{
    class Program
    {
        public class Stec
        {
            int[] S = new int[100];
            int top = 0;
            public void PUSH(int x)
            {
                S[top] = x;
                top++;
            }
            public bool POP()
            {
                if (!ISEMPTY())
                {
                    S[top - 1] = -1;
                    return true;
                }
                else
                {
                    return false;
                }
            }
            public bool ISEMPTY()
            {
                if (top == 0)
                {
                    return true;
                }
                else
                {
                    return false;
                }
            }
            public void CLAER()
            {
                int n = 0;
                while (S[n] != -1)
                {
                    n++;
                    S[n] = -1;
                }
            }
            public int TOP()
            {
                return S[top - 1];
            }
        }

        static void Main(string[] args)
        {
            Stec S = new Stec();
            S.PUSH(10);
            S.PUSH(10);
            S.PUSH(10);
            S.PUSH(10);
            S.POP();
            Console.WriteLine(S.TOP());
            S.CLAER();
            Console.WriteLine(S.ISEMPTY());
            Console.WriteLine("Hello World!");
        }
    }
}