diff --git a/6.rkt b/6.rkt
index 65929a7..c0a5c85 100644
--- a/6.rkt
+++ b/6.rkt
@@ -7,7 +7,7 @@
 (define (do-race time dist)
   (match-define (list lower upper)
     (quadratic-solutions 1 (- time) dist))
-  (inexact->exact (- (ceiling upper) (add1 (floor lower)))))
+  (inexact->exact (- (ceiling upper) (floor lower) 1)))
 
 (define (part1 input)
   (for/product ([time (in-list (first input))]