import java.util.StringTokenizer;
   import java.io.*;  // for I/O

    public class ReversePolishTest
   {
      static BufferedReader keyboard = new BufferedReader 
      								    	(new InputStreamReader (System.in));
   
      static MyStringStack S;
   
       public static void main(String[] args) throws IOException
      {
         System.out.println ("Please enter an anrithmetic expression in reverse polish notation" 
            		+ "\nusing only multiplication and addition.");
      
      // parse the input and output to the user
         StringTokenizer tokenizer = new StringTokenizer(keyboard.readLine());
      	
         S = new MyStringStack();
			
			//push the expression onto the stack.
			while (tokenizer.hasMoreTokens())
			{
				S.push(tokenizer.nextToken());
			}
			
			
      	System.out.println("The result of the expression is " + getExpr(S) + ".");
      	
      
      }
		
		//pops an expression off of the stack and returns the evaluation of it.
		public static int getExpr(MyStringStack S)
		{
			String op = S.top();
			S.pop();
			
			if (op.equals("+"))
			{
				int a = getExpr(S);
				int b = getExpr(S);
				return a + b;
			}
			else if (op.equals("*"))
			{
				int a = getExpr(S);
				int b = getExpr(S);
				return a*b;
			}
			else 
				return Integer.valueOf(op).intValue();
		}
   
   }