import java.io.*;
import java.util.*;

public class Solution {

    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        int Q = Integer.parseInt(reader.readLine());
        StringBuilder S = new StringBuilder(); 
        Stack<String> stack = new Stack<>(); 
        while (Q-- > 0) {
            String[] input = reader.readLine().split(" ");
            int type = Integer.parseInt(input[0]);

            switch (type) {
                case 1: 
                    stack.push(S.toString()); 
                    S.append(input[1]);
                    break;

                case 2: 
                    int k = Integer.parseInt(input[1]);
                    stack.push(S.toString()); 
                    S.delete(S.length() - k, S.length());
                    break;

                case 3: 
                    int index = Integer.parseInt(input[1]);
                    System.out.println(S.charAt(index - 1));
                    break;

                case 4: 
                    if (!stack.isEmpty()) {
                        S = new StringBuilder(stack.pop());
                    }
                    break;
            }
        }
    }
}