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

class Solution {
    static class Pair
	{
		//to store the write and delete commands and operated strings in a stack
		int opr;
		String text;
		Pair(int op, String s)
		{
			opr = op;
			text = s;
		}
	}
	public void SimpleTextEditor()
	{
        Scanner sc = new Scanner(System.in);

		//first line of input has length of string array
		int n = Integer.parseInt(sc.nextLine().trim());
		String[] operations = new String[n];

		for(int i = 0; i < n; i++)
			operations[i] = sc.nextLine();

		//create stack to store operations of write and delete and string builder to store text
		Stack<Pair> st = new Stack<>();
		StringBuilder doc = new StringBuilder();

		for(int i = 0; i < n; i++)
		{
			int command = operations[i].charAt(0) - '0';
			if(command == 1)//append
			{
				String text = operations[i].substring(2);
				st.push(new Pair(1, text));
				doc.append(text);
			}
			else if(command == 2)//delete
			{
				int length = Integer.parseInt(operations[i].substring(2));
				int startDelete = doc.length() - length;
				int endDelete = doc.length();		
				
				st.push(new Pair(2, doc.substring(startDelete)));
				doc.delete(startDelete, endDelete);
			}
			else if(command == 3)//print
			{
				int index =Integer.parseInt(operations[i].substring(2)) - 1;
				System.out.println(doc.charAt(index));
			}
			else if(command == 4)//undo
			{
				Pair last = st.pop();
					if(last.opr == 1)
					{
						int textlength = last.text.length();
						int deleteStart = doc.length() - textlength;
						doc.delete(deleteStart, doc.length());
					}
					else if(last.opr == 2)
					{
						String deleted = last.text;
						doc.append(deleted);
					}
			}
			else
				System.out.println("INVALID");
						
		}
    }
}

public class Main {
    public static void main(String args[]) {
        Solution ob = new Solution();
        ob.SimpleTextEditor();
    }
}