Maximum Element

import java.util.Scanner;
import java.util.Stack;

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

        int commandsNum = sc.nextInt();
        Stack<Integer> stack = new Stack<>(), maxStack = new Stack<>();
        int maxNumber = 0;
        for (int i = 0; i < commandsNum; i++) {
            int command = sc.nextInt();
            if (command == 1) {
                int value = sc.nextInt();
                if (maxNumber <= value) {
                    maxNumber = value;
                    maxStack.push(maxNumber);
                }
                stack.push(value);
            } else if (command == 2) {
                if (stack.pop() == maxNumber) {
                    maxStack.pop();
                    if (maxStack.size() > 0) {
                        maxNumber = maxStack.peek();
                    } else {
                        maxNumber = 0;
                    }
                }
            } else {
                System.out.println(maxNumber);
            }
        }
    }
}