diff --git a/scripts/aoc.rkt b/scripts/aoc.rkt
index 96040c4..5b98d97 100644
--- a/scripts/aoc.rkt
+++ b/scripts/aoc.rkt
@@ -44,7 +44,9 @@
   (define num-first-lefts
     (for/sum ([m (in-list matching)] #:when (set-member? left (first m)))
       1))
-  (if (> num-first-lefts (/ (set-count left) 2))
+  ;; if the first set contains more elements belonging to lefts than rights, then assume it's in
+  ;; the right order. otherwise, swap
+  (if (> num-first-lefts (- (length matching) num-first-lefts))
     matching
     (map #{list (second %) (first %)} matching)))