Corrected tracing.

diff --git a/npc.lisp b/npc.lisp
index 6e01f07..59fd4e7 100644
--- a/npc.lisp
+++ b/npc.lisp
@@ -236,7 +236,8 @@
                              (print c)
                              (print m)
                              (<- a (+ 4 (* (+ 6 (* (+ 9 (* (+ 1 (* 0 d)) d)) d)) d)))
-                             (print a)))))
+                             (print a))))
+        :trace t)
 ;; prints:
 ;; 10
 ;; 100