using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Problem_9._Simple_Text_Editor
{
    class Program
    {
        static void Main(string[] args)
        {
            var count = int.Parse(Console.ReadLine());

            var text = string.Empty;

            var stack = new Stack<string>();

            for (int i = 0; i < count; i++)
            {
                var input = Console.ReadLine().Split().ToArray();

                var index = int.Parse(input[0]);

                if (index == 1)
                {
                    stack.Push(text.ToString());
                    text += input[1];
                }
                else if (index == 2)
                {
                    var length = int.Parse(input[1]);

                    stack.Push(text.ToString());
                    text = text.Substring(0, text.Length - length);
                }
                else if (index == 3)
                {
                    var printedElement = int.Parse(input[1]);
                    Console.WriteLine(text[printedElement - 1]);
                }
                else if(index == 4)
                {
                    text = stack.Pop();
                }

            }

        }
    }
}