import java.io.*;

import java.util.*;

public class TextEditor {

static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

public static int nextInt() throws IOException {

return Integer.parseInt(br.readLine());

}

public static int[] nextArr() throws IOException {

String elements[] = br.readLine().split(" ");

int arr[] = new int[elements.length];

for (int j = 0; j < elements.length; j++)

arr[j] = Integer.parseInt(elements[j]);

return arr;

}

public static void printArr(int arr[]) {

for (int i = 0; i < arr.length; i++)

System.out.print(arr);

}

public static String next() throws IOException {

return br.readLine();

}

public static void left(String s) {

// First left non repeating character

int arr[] = new int[256];

int ans = Integer.MAX_VALUE;

for (int i = 0; i < s.length(); i++)

arr[s.charAt(i)]++;

for (int i = 0; i < arr.length; i++) {

if (arr[i] == 1) {

ans = Math.min(ans, s.indexOf((char) i));

}

}

System.out.println(ans == Integer.MAX_VALUE ? -1 : s.charAt(ans) + "");

}

public static void main(String[] args) throws IOException {

Stack<String> st = new Stack<String>();

st.push("");

int T = nextInt();

while (T-- > 0) {

String input[] = br.readLine().split(" ");

int choice = Integer.parseInt(input[0]);

int operation = 0;

if (choice != 4 && choice != 1)

operation = Integer.parseInt(input[1]);

if (choice == 1) {

st.push(st.peek() + input[1]);

} else if (choice == 2) {

String curr = st.peek().substring(0, st.peek().length() - operation);

st.push(curr);

} else if (choice == 3) {

if (!st.isEmpty())

System.out.println(st.peek().charAt(operation - 1));

else

System.out.println("");

} else {

if (!st.isEmpty())

st.pop();

}

System.out.println(st.peek());

left(br.readLine());

}

}

}