(define (cons x y)
  (* (expt 2 x) (expt 3 y)))

(define (is-factor? d n)
  (and (= (remainder n d) 0)
       (not (= n 0))))

(define (car z)
  (if (is-factor? 2 z)
      (+ 1 (car (/ z 2)))
      0))

(define (cdr z)
  (if (is-factor? 3 z)
      (+ 1 (cdr (/ z 3)))
      0))