import java.io.*;
import java.util.*;


public class Main {

    static PrintWriter pw;

    public static void main(String[] args) throws FileNotFoundException {
        Scanner in = new Scanner(new File("input.txt"));
        pw = new PrintWriter(new File("output.txt"));


        Stack<Integer> stack = new Stack<>();

        while (in.hasNext()) {
            String a = in.next();
            switch (a){
                case "*":
                    stack.push(stack.pop() * stack.pop());
                    break;
                case "+":
                    stack.push(stack.pop() + stack.pop());
                    break;
                case "-":
                    stack.push(-stack.pop() + stack.pop());
                    break;
                default:
                    stack.push(Integer.parseInt(a));
            }
        }
        pw.println(stack.pop());
        pw.close();

    }


}