(define (recur-cycle n)
 (define (div_2_5 x)
  (cond 
   ((= (remainder x 2) 0)
	(div_2_5 (/ x 2)))
   ((= (remainder x 5) 0)
	(div_2_5 (/ x 5)))
   (else x)))
 (define (try-iter m r)
  (if (= r 1)
   m
   (try-iter (+ m 1) (remainder (* r 10) n))))
 (if (= (div_2_5 n) n)
  (if (= n 1)
   0
   (try-iter 1 (remainder 10 n)))
  (recur-cycle (div_2_5 n))))

(define (longest upper)
 (define (try-iter n ans anscycle)
  (if (> n upper)
   ans
   (let ((m (recur-cycle n)))
	 (if (> m anscycle)
	  (try-iter (+ n 1) n m)
	  (try-iter (+ n 1) ans anscycle)))))
 (try-iter 1 1 0))

(display (longest (read)))
(newline)