/* The grammar below is correct, but you're never going to get rid
 * of the ambiguities...  
 * The best bet would be to code the whole thing directly in Java.
 */

options {
  LOOKAHEAD=1;
}


PARSER_BEGIN(Q2)

public class Q2 {

  /*** Main routine - just call parser ***/
  public static void main(String args[]) throws ParseException {
    Q2 parser = new Q2(System.in);
    try {
      parser.inp_string();
      System.out.println("Is a palindrome!");
    } catch (ParseException x) {
      System.out.println("Is not a palindrome");
      // Let's not throw x;  
    }
  }

}

PARSER_END(Q2)


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

 

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


void inp_string() :
{}
{
  pal() ( <EOF> | "\n" | "\r")
}

void pal() :
{}
{
  "a" [ pal() "a" ]
| "b" [ pal() "b" ]
| "c"
}