using System;
using System.Collections.Generic;
using System.IO;
using System.Text;

class Editor {
    private StringBuilder _sb = new StringBuilder();
    private Stack<Action> _history = new Stack<Action>();
    
    public void Append(string s) {
        int start = _sb.Length;
        int len = s.Length;
        _history.Push(() => _sb.Remove(start, len));
        _sb.Append(s);
    }
    
    public void DeleteLast(int n) {
        string last = Substring(_sb.Length - n);
        _history.Push(() => _sb.Append(last));
        _sb.Remove(_sb.Length - n, n);
    }
    
    private string Substring(int start) {
        char[] buffer = new char[_sb.Length - start];
        
        for (int i = 0, j = start; j < _sb.Length; i++, j++)
            buffer[i] = _sb[j];
            
        return new string(buffer);
    }
    
    public char GetChar(int n) =>_sb[n - 1];
    
    public void Undo() {
        if (_history.Count > 0)
            _history.Pop()();
    }
}

class Solution {
    static void Main(String[] args) {
        var editor = new Editor();
        
        int q = Convert.ToInt32(Console.ReadLine());
        
        for (int i = 0; i < q; i++) {
            string[] parts = Console.ReadLine().Split(' ');
            int cmd = Convert.ToInt32(parts[0]);
            int k;
            
            switch (cmd) {
                case 1:
                    editor.Append(parts[1]);
                    break;
                    
                case 2:
                    k = Convert.ToInt32(parts[1]);
                    editor.DeleteLast(k);
                    break;
                
                case 3:
                    k = Convert.ToInt32(parts[1]);
                    char c = editor.GetChar(k);
                    Console.WriteLine(c);
                    break;
                    
                case 4:
                    editor.Undo();
                    break;
            }
        }
    }
}