08. Simple Text Editor

import java.util.ArrayDeque;
import java.util.Scanner;

public class SimpleTextEditor {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        int n = Integer.parseInt(scanner.nextLine());

        ArrayDeque<String> stack = new ArrayDeque<>();

        for (int i = 0; i < n ; i++) {
            String [] token = scanner.nextLine().split(" ");

            switch (token[0]){
                case "1":
                    stack.push(token[1]);
                    break;
                case "2":
                    stack.push(stack.peek().substring(0,  stack.peek().length() - Integer.parseInt(token[1])));
                    break;
                case "3":
                    System.out.println(stack.peek().charAt(Integer.parseInt(token[1]) - 1));
                    break;
                case "4":
                    stack.pop();
                    break;
            }
        }
    }
}