// Calc.C
// (c) Burton Rosenberg 1996
// Small program to write a stack-based calculator

#include<iostream.h>
#include<stdlib.h>

class Node {
public:
   int item ;
   Node * next ;
} ;

class List {
private:
   Node * anchor ;
public:
   void init(void) ;
   void push(int i) ;
   void print(void) ;
   int pop(void) ;
} ;

void List::
init ( void )
{
   anchor = NULL ;
}

void List::
push( int i )
{
    Node * n = new Node ;
    n->item = i ;
    n->next = anchor ;
    anchor = n ;
}

void List::
print( void )
{
    Node * n = anchor ;
    while ( n != NULL ) {
       cout << n->item << endl ;
       n = n->next ;
    }
}

int List::
pop( void )
{
   int i ;
   Node * p ;
   if ( anchor==NULL) return 0 ;
   p = anchor ;
   anchor = anchor->next ;
   i = p->item ;
   delete p ;
   return i ;
}

enum CMDTYPE { Number, Plus, Minus, Times, Divide, Quit, Error, Nothing } ;

CMDTYPE identify( char s[] ) 
{
   switch(s[0]) {
   case '0':
   case '1':
   case '2':
   case '3':
   case '4':
   case '5':
   case '6':
   case '7':
   case '8':
   case '9':
             return Number ;
   case '+': return Plus ;
   case '-': return Minus ;
   case '*': return Times ;
   case '/': return Divide ;
   case 'q':
   case 'Q':
             return Quit ;
   default :
             return Error ;
   }
}

int value( char s[] ) 
{
   return (s[0]-'0') ;
}

void main() {
   int a, b ;
   List myList ;
   myList.init() ;
   CMDTYPE c = Nothing ;
   char inputLine[100] ;

   while ( c != Quit ) 
   {
      cin.getline(inputLine, 100) ;
      switch( c = identify(inputLine) ) 
      {
      case Number:
           myList.push(value(inputLine)) ;
           break ;
      case Plus:
           a = myList.pop() ;
           b = myList.pop() ;
           cout << "= " << a+b << endl ;
           myList.push(a+b) ;
           break ;
      case Minus:
           a = myList.pop() ;
           b = myList.pop() ;
           cout << "= " << b-a << endl ;
           myList.push(b-a) ;
           break ;
      case Times:
           a = myList.pop() ;
           b = myList.pop() ;
           cout << "= " << a*b << endl ;
           myList.push(a*b) ;
           break ;
      case Divide:
           a = myList.pop() ;
           b = myList.pop() ;
           cout << "= " << a/b << endl ;
           myList.push(a/b) ;
           break ;
      }
   }
}