AiSD1_1

using System;

namespace AiSD1
{
    class Program
    {
        void PUSH(int x, int[] S)
        {
            int n = 0;
            while(S[n] != -1)
            {
                n++;
            }
            S[n] = x;
        }
        bool POP(int[] S)
        {
            if (!ISEMPTY(S))
            {
                int n = 0;
                while (S[n] != -1)
                {
                    n++;
                }
                S[n] = -1;
                return true;
            }
            else
            {
                return false;
            }
        }
        bool ISEMPTY(int[] S)
        {
            if(S[0] == -1)
            {
                return true;
            }
            else
            {
                return false;
            }
        }
        void CLAER(int[] S)
        {
            int n = 0;
            while (S[n] != -1)
            {
                n++;
                S[n] = -1;
            }
        }
        int TOP(int[] S)
        {
            int n = 0;
            while (S[n] != -1)
            {
                n++;
            }
            return S[n - 1];
        }
        static void Main(string[] args)
        {
            Console.WriteLine("Hello World!");
        }
    }
}