class ABCDEF{


  public static void main(String[] args) {
      enigma("DOG");
    }

    static void enigma (String s) {
      int len = s.length();
      if(s == null|| len <= 1) {
        System.out.print(s);
        return;
      }
      else{
        System.out.print(s.charAt(len-1)) ;
        enigma(s.substring(0, len-1));
      }
    }
  }