public static void main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
        Scanner input = new Scanner(System.in);
        int q = input.nextInt();
        
        Stack<String> stack = new Stack<>();
        StringBuilder sb = new StringBuilder();
        
        for(int j = 0; j < q; j++) {
            int choose = input.nextInt();
            switch(choose) {
                case 1:
                    stack.push(sb.toString());
                    String newText = input.next();
                    sb.append(newText);
                    break;
                case 2:
                    stack.push(sb.toString());
                    int k = input.nextInt();
                    sb.delete(sb.length() - k, sb.length());
                    break;
                case 3:
                    int kth = input.nextInt();
                    System.out.println(sb.charAt(kth - 1));
                    break;
                case 4:
                    sb.setLength(0);
                    sb.append(stack.pop());
                    break;
            }
        }
    }