PARSER_BEGIN(Q2)

class Q2 {


  /** Standard code to call the parser
   */
  public static void main(String args[]) {

    Q2 parser;

    System.out.println("Reading from standard input . . .");
    parser = new Q2(System.in);
    try {
      int res = parser.s();
      System.out.println("The answer is: "+res);
     } catch (ParseException e) {
      System.out.println("Encountered errors during parse.");
    }
  }   /* End of function "main" */


}

PARSER_END(Q2)



/******************/
/***** TOKENS *****/
/******************/

SKIP : /* WHITE SPACE */
{
  " " 
| "\t"
| "\n"
| "\r"
}

TOKEN : 
{
  < PLUS : "+" >
| < MINUS : "-" >
| < TIMES : "*" >
| < DIVIDE : "/" >
| < NUM : (<DIGIT>)+ >
| < #DIGIT : ["0"-"9"] >
}
 

/*************************/
/***** GRAMMAR RULES *****/
/*************************/

int s() :
{
  int i;
}
{
  i=e() <EOF> { return i; }
}

int e() : 
{
  Token t;
  int i1, i2, oper;
}
{
  t=<NUM> 
     { i1 = Integer.parseInt(t.image); }
  ( i2=e() oper=o() 
     { switch (oper) {
          case 1: i1 += i2; break;
          case 2: i1 -= i2; break;
          case 3: i1 *= i2; break;
          case 4: i1 /= i2; break;
       }
     }
  )*
  { return i1; }
}
    
int o() : {}
{
  <PLUS> { return 1; }
| <MINUS> { return 2; }
| <TIMES> { return 3; }
| <DIVIDE> { return 4; }
}