diff --git a/4.rkt b/4.rkt
index eadf078..8132ee1 100644
--- a/4.rkt
+++ b/4.rkt
@@ -5,16 +5,10 @@
 ;; solution for day 4
 
 (define (part1 input)
-  (for*/sum ([line (in-list input)]
-             [u (in-value (apply is:union line))]
-             #:when (member u line))
-    1))
+  (count #{member (apply is:union %) %} input))
 
 (define (part2 input)
-  (for*/sum ([line (in-list input)]
-             [i (in-value (apply is:intersect line))]
-             #:unless (zero? (is:count i)))
-    1))
+  (count #{is:get-integer (apply is:intersect %)} input))
 
 (define (parse fname)
   (for/list ([line (in-list (file->lines fname))])