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

public class Main {
    public static void main(String[] args) {
        CalculatorFunction function = new CalculatorFunction();
        Stack<Integer> numbers = new Stack<>();
        Scanner scanner = new Scanner(System.in);
        String[] input = {"\n"};
        while (!input[0].equals("quit")){
            input = scanner.nextLine().split(" ");
            switch (input[0]){
                case "push":
                    try {
                        if(input.length > 2){
                            System.out.println(input.length);
                            System.out.println("Too much arguments passed");
                            break;
                        }
                        int n = Integer.parseInt(input[1]);
                        numbers.push(n);
                        System.out.println("OK");
                    }catch (NumberFormatException ex){
                        System.out.println("Enter valid number");
                    }
                    break;
                case "pop":
                    if(input.length >= 2){
                        System.out.println("Too much arguments passed");
                    }
                    else if(numbers.isEmpty()){
                        System.out.println("Stack is empty");
                    }
                    numbers.pop();
                    System.out.println("OK");
                    break;
                case "peek":
                    if(input.length >= 2){
                        System.out.println("Too much arguments passed");
                    }
                    else if(numbers.isEmpty()){
                        System.out.println("Stack is empty");
                    }
                    System.out.println(numbers.peek());
                    break;
                case "add":
                    if(input.length > 1){
                        System.out.println("Too much arguments passed");
                    }
                    else if(numbers.size() >= 2) {
                        numbers.add(function.operation(numbers.lastElement(), numbers.get(numbers.size() - 2), "+"));
                        System.out.println("OK");
                    }
                    else{
                        System.out.println("Not enough numbers in stack");
                    }
                    break;
                case "sub":
                    if(input.length > 1){
                        System.out.println("Too much arguments passed");
                    }
                    else if(numbers.size() >= 2) {
                        numbers.add(function.operation(numbers.get(numbers.size() - 2), numbers.lastElement(), "-"));
                        System.out.println("OK");
                    }
                    else{
                        System.out.println("Not enough numbers in stack");
                    }
                    break;
                case "multiply":
                    if(input.length > 1){
                        System.out.println("Too much arguments passed");
                    }
                    else if(numbers.size() >= 2) {
                        numbers.add(function.operation(numbers.lastElement(), numbers.get(numbers.size() - 2), "*"));
                        System.out.println("OK");
                    }
                    else{
                        System.out.println("Not enough numbers in stack");
                    }
                    break;
                case "divide":
                    if(input.length > 1){
                        System.out.println("Too much arguments passed");
                    }
                    else if(numbers.size() >= 2) {
                        numbers.add(function.operation(numbers.lastElement(), numbers.get(numbers.size() - 2), "/"));
                        System.out.println("OK");
                    }
                    else{
                        System.out.println("Not enough numbers in stack");
                    }
                    break;
                case "if-else":
                    if(numbers.size() >= 3) {
                        if(numbers.lastElement() != 0){
                            numbers.get(numbers.size() - 1);
                            System.out.println("OK");
                        }
                        else if(numbers.get(numbers.size() - 2) != 0){
                                numbers.get(numbers.size() - 2);
                                System.out.println("OK");
                        }
                        else {
                            numbers.get(numbers.size() - 3);
                            System.out.println("OK");
                        }

                    }
                    else{
                        System.out.println("Not enough numbers in stack");
                    }
                    break;
                case "print":
                    if(input.length > 1){
                        System.out.println("Too much arguments passed");
                    }
                    for (int i = numbers.size() ; i > 0; i--){
                        if(i > 1){
                            System.out.print(numbers.get(i - 1) + ",");
                        }
                        else{
                            System.out.println(numbers.get(0));
                        }
                    }
                    break;
                case "revert":
                    if(input.length > 1){
                        System.out.println("Too much arguments passed");
                    }
                    for(int i = 0; i <= numbers.size(); i++){
                        numbers.insertElementAt(numbers.get(numbers.size() - 1),i);
                        numbers.pop();
                    }
                    System.out.println("OK");
                    break;
                case "reset":
                    if(input.length > 1){
                        System.out.println("Too much arguments passed");
                    }
                    numbers.clear();
                    System.out.println("OK");
            }
        }
    }
}