//문제 3. 다음 프로그램의 출력을 쓰시오.

using System;

namespace Test3
{
    class Stack
    {
        int[] s;
        public Stack()
        {
            s = new int[2];
        }
        public void push(int x)
        {
            int[] ss = new int[s.Length + 2];
            for (int i = 0; i < s.Length; i++)
            {
                ss[2 + i] = s[i];
            }
            ss[0] = x;
            ss[1] = x;
            s = ss;
        }
        public void pop()
        {
            s[0] = 0;
        }
        public void print()
        {
            for (int i = 0; i < s.Length; i++)
            {
                Console.Write(s[i]);
            }
            Console.WriteLine();
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            int[] data = { 1, 2, 3, 4, 5 };
            Stack stack = new Stack();

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