import java.util.*;
import java.util.function.Function;

public class RpnCalculator {

    private static Map<String, Function<Deque<Integer>, Integer>> operations = new HashMap<>();

    static {
        operations.put("+", deque -> deque.pop() + deque.pop());
        operations.put("-", deque -> deque.removeLast() - deque.pop());
        operations.put("*", deque -> deque.pop() * deque.pop());
        operations.put("/", deque -> deque.removeLast() / deque.pop());
        operations.put("SQRT", deque -> (int) Math.sqrt(deque.pop()));
        operations.put("MAX", deque -> deque.stream().max(Integer::compareTo).orElseThrow(() -> new IllegalArgumentException("No Numbers Provided Before MAX")));
    }

    static public int calculate(String expression) {
        String[] tokens = expression.split(" ");

        Deque<Integer> numbers = new ArrayDeque<>();
        Arrays.stream(tokens).forEach(token -> {
            if (operations.containsKey(token)) {
                numbers.push(operations.get(token).apply(numbers));
            } else {
                numbers.push(Integer.valueOf(token));
            }
        });

        return numbers.pop();
    }
}