import java.util.*;
/**
 * Simple illustration of postfix evaluation using
 * StringTokenizer, Stack, and Exceptions.
 * @author Owen Astrachan
 * @date revised Oct 7, 2009
 * original from 2004
 */

public class Postfix {

	private static final String DELIMS = "+-*/ ";
	
	private int operate(String op, int lhs, int rhs){
		if (op.equals("+")) {
			return lhs + rhs;
		}
		if (op.equals("*")){
			return lhs * rhs;
		}
		if (op.equals("-")){
			return lhs - rhs;
		}
		if (op.equals("/")){
			return lhs / rhs;
		}
		throw new IllegalArgumentException("unrecognized operator "+op);
	}
	
	public int evaluate(String s){
		Stack<String> stack = new Stack<String>();
		StringTokenizer tokens = new StringTokenizer(s,DELIMS,true);
		try {
			while (tokens.hasMoreTokens()){
				String t = tokens.nextToken();
				if (DELIMS.indexOf(t) >= 0){
					
					if (t.equals(" ")) continue;
					
					int right = Integer.parseInt(stack.pop());
					int left = Integer.parseInt(stack.pop());
					stack.push(""+operate(t,left,right));
				}
				else {
					stack.push(t);
				}
			}
		} catch (NumberFormatException e) {
			throw new RuntimeException("badly formed postfix expression "+e);
		}
		catch (EmptyStackException ese){
			throw new RuntimeException("empty stack error "+ese);
		}
		int result = Integer.parseInt(stack.pop());
		if (stack.size() > 0){
			throw new IllegalArgumentException("non empty stack on "+s);
		}
		return result;
	}
	
	public void readLoop(){
		Scanner in = new Scanner(System.in);
		String line;
		while (in.hasNextLine()){
			line = in.nextLine();
			try {
				int result = evaluate(line);
				System.out.printf("value of %s = %d\n", line,result);
			}
			catch (Exception e){
				System.out.printf("error: %s\n",e);
			}
		}
	}
	
	public static void main(String[] args){
		Postfix p = new Postfix();
		p.readLoop();
	}
}