/* This wasn't part of the question, but it provides an interesting
 * contrast to the infix-to-prefix version...
 * Notice how here we don't have to store anything in a string as
 * we go along - instead we can just print it out directly, expression
 * by expression
 */

options {
  LOOKAHEAD=1;
}


PARSER_BEGIN(Q3post)

public class Q3post {

  /*** Main routine - just call parser ***/
  public static void main(String args[]) throws ParseException {
    Q3post parser = new Q3post(System.in);
    try {
      parser.inp_line();
      System.out.flush();
    } catch (ParseException x) {
      System.out.println("Exiting due to parse error.");
      throw x;
    }
  }

}

PARSER_END(Q3post)


SKIP : /*** Ignoring spaces/tabs ***/
{
    " "
  | "\t"
}

 

TOKEN :
{
  < NUMBER : ( ["0"-"9"] )+ >
}


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


void inp_line() :
{}
{
  expr() ( <EOF> | "\n" | "\r")
}

void expr() :
{}
{
  term() ( "+" term() { System.out.print("+ "); } )*
}

void term() :
{}
{
  factor() ( "*" factor() { System.out.print("* "); } )*
}

void factor() :
{}
{
  <NUMBER> { System.out.print(token.image+" "); }
| "(" expr() ")"
}