//¹®Á¦ 2. ´ÙÀ½ ÇÁ·Î±×·¥ÀÇ Ãâ·ÂÀ» ¾²½Ã¿À.

using System;

namespace Test2
{
    class Stack
    {
        int[] s;
        int top;
        int pos;
        public Stack() {
            s = new int[10];
            top = -1;
            pos = s.Length / 2;
        }
        public void push(int x) {
            top++;
            s[pos + top] = x;
            s[pos - top] = x;
        }
        public int pop() {
            s[pos + top] = 0;
            s[pos - top] = 0;
            top--;
            return s[top];
        }
        public void print() {
            for (int i = 0; i < s.Length; i++) {
                if (s[i] != 0) Console.Write(s[i]);
            }
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            int[] data = { 1, 2, 3, 4, 5 };
            Stack s = new Stack();

            for (int i = 0; i < data.Length; i++) {
                s.push(data[i]);
            }
            s.pop();
            s.pop();
            s.print();
        }
    }
}