import java.io.StringReader;
import java.util.Scanner;
import java.util.Stack;

public class RPN {
    Stack<Integer> stack = new Stack<Integer>();

    Stack<Integer> evaluate(String expression) {
        StringReader sr = new StringReader(expression);
        Scanner scanner = new Scanner(sr);
        while (scanner.hasNext()) {
            String token = scanner.next();
            if (token.equals("+")) {
                int a = stack.peek();
                stack.pop();
                int b = stack.peek();
                stack.pop();
                stack.push(a + b);
            } else if (token.equals("-")) {
                int a = stack.peek();
                stack.pop();
                int b = stack.peek();
                stack.pop();
                stack.push(a - b);
            } else if (token.equals("")) {
                int a = stack.peek();
                stack.pop();
                int b = stack.peek();
                stack.pop();
                stack.push(a * b);
            } else if (token.equals("/")) {
                int a = stack.peek();
                stack.pop();
                int b = stack.peek();
                stack.pop();
                stack.push(a / b);
            } else {
                stack.push(Integer.parseInt(token));
            }
        }
        return stack;
    }

    void clear() {
        stack.clear();
    }
}