diff --git a/13-transparent-origami/code.scm b/13-transparent-origami/code.scm
index c497a1c..b10d11a 100644
--- a/13-transparent-origami/code.scm
+++ b/13-transparent-origami/code.scm
@@ -35,21 +35,16 @@
 ; mirrors coordinates along given axis and line/column
 ; returns a new list of coordinates
 (define (fold coords axis-position)
-  (let* [(axis (car axis-position))
-	 (position (cadr axis-position))
-	 (position*2 (* 2 position))]
-    (define (mirror-x x y) (list (if (> x position) (- position*2 x) x) y))
-    (define (mirror-y x y) (list x (if (> y position) (- position*2 y) y)))
-    (let [(mirror (if (char=? axis #\x) mirror-x mirror-y))]
-      (define (folder output coord)
-	(let* [(x (car coord))
-	       (y (cadr coord))
-	       (mirrored (mirror x y))]
-	  ; add mirrored coord only if it wasn't in output already
-	  (if (member mirrored output) 
-	    output
-	    (cons (mirror x y) output))))
-      (fold-left folder '() coords))))
+  (let-values [((axis position) (apply values axis-position))]
+    (let [(position*2 (* position 2))]
+      (define (mirror-x x y) (list (if (> x position) (- position*2 x) x) y))
+      (define (mirror-y x y) (list x (if (> y position) (- position*2 y) y)))
+      (let [(mirror (if (char=? axis #\x) mirror-x mirror-y))]
+	(define (folder output coord)
+	  (let* [(mirrored (apply mirror coord))]
+	    ; add mirrored coord only if it wasn't in output already
+	    (if (member mirrored output) output (cons mirrored output))))
+	(fold-left folder '() coords)))))
 
 (call-with-input-file
   "input"