x = ['']
for s in [input() for _ in range(int(input()))]:
    x.append(x[-1]+s[2:]) if s[0] == '1' else x.append(x[-1][:-int(s[2:])]) if s[0] == '2' else print(x[-1][int(s[2:])-1]) if s[0] == '3' else x.pop() if s == '4' else ...

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;
            }
        }
    }
}

class Editor:
    def __init__(self):
        """Initialize the text editor."""
        self.text = ""
        self.history = []

    def append(self, word):
        """Append a word to the end of the text."""
        self.history.append(self.text)
        self.text += word

    def delete(self, k):
        """Delete the last k characters from the text."""
        if 0 <= k <= len(self.text):
            self.history.append(self.text)
            self.text = self.text[:-k]
        else:
            raise ValueError("Cannot delete more characters than the length of the text.")

    def print_char(self, k):
        """Print the character at the specified index in the text."""
        if 1 <= k <= len(self.text):
            print(self.text[k - 1])
        else:
            raise IndexError("Index out of range.")

    def undo(self):
        """Undo the last operation by restoring the previous state of the text."""
        if self.history:
            self.text = self.history.pop()
        else:
            print("Nothing to undo.")

# Test the Editor class
editor = Editor()
count = int(input())
for _ in range(count):
    operation = input().split()
    op_code = operation[0]
    try:
        if op_code == '1':
            editor.append(operation[1])
        elif op_code == '2':
            editor.delete(int(operation[1]))
        elif op_code == '3':
            editor.print_char(int(operation[1]))
        elif op_code == '4':
            editor.undo()
        else:
            print("Invalid operation code.")
    except (ValueError, IndexError) as e:
        print(f"Error: {e}")