diff --git a/mu.arc b/mu.arc
index e4f22ce1..72a0d86c 100644
--- a/mu.arc
+++ b/mu.arc
@@ -3148,6 +3148,15 @@
   (reply result:terminal-address)
 )
 
+(init-fn divides?
+  (default-space:space-address <- new space:literal 30:literal/capacity)
+  (x:integer <- next-input)
+  (y:integer <- next-input)
+  (_ remainder:integer <- divide-with-remainder x:integer y:integer)
+  (result:boolean <- equal remainder:integer 0:literal)
+  (reply result:boolean)
+)
+
 ; after all system software is loaded:
 ;? (= dump-trace* (obj whitelist '("cn0" "cn1")))
 (freeze system-function*)
@@ -3186,7 +3195,8 @@
 (when (no cdr.argv)
   (add-code:readfile "trace.mu")
   (wipe function*!main)
-  (add-code:readfile "chessboard.mu")
+  (add-code:readfile "factorial.mu")
+;?   (add-code:readfile "chessboard.mu")  ; takes too long
   (wipe function*!main)
   (freeze function*)
   (load-system-functions)
diff --git a/trace.mu b/trace.mu
index ad8c306c..b327a1d6 100644
--- a/trace.mu
+++ b/trace.mu
@@ -22,6 +22,7 @@
 ;?   ($print (("parse-traces\n" literal))) ;? 2
   (in:stream-address <- next-input)
   ; check input size
+  ($print (("counting lines\n" literal)))
   (n:integer <- copy 0:literal)
   { begin
     (done?:boolean <- end-of-stream? in:stream-address)
@@ -31,6 +32,13 @@
       (newline?:boolean <- equal c:character ((#\newline literal)))
       (break-unless newline?:boolean)
       (n:integer <- add n:integer 1:literal)
+      { begin
+;?         (print?:boolean <- divides? n:integer 100:literal)
+;?         (break-unless print?:boolean)
+        ($print ((" " literal)))
+        ($print n:integer)
+        ($print (("\n" literal)))
+      }
     }
     (loop)
   }
@@ -42,6 +50,8 @@
   (curr-tail:instruction-trace-address <- copy nil:literal)
   (ch:buffer-address <- init-buffer 5:literal)  ; accumulator for traces between instructions
   (run:string-address/const <- new "run")
+  ($print (("parsing\n" literal)))
+  (n:integer <- copy 0:literal)
   ; reading each line from 'in'
   { begin
     next-line
@@ -51,6 +61,14 @@
     (break-if done?:boolean)
     ; parse next line as a generic trace
     (line:string-address <- read-line in:stream-address)
+    { begin
+      (n:integer <- add n:integer 1:literal)
+      (print?:boolean <- divides? n:integer 100:literal)
+      (break-unless print?:boolean)
+      ($print ((" " literal)))
+      ($print n:integer)
+      ($print (("\n" literal)))
+    }
 ;?     (print-string nil:literal/terminal line:string-address) ;? 1
     (f:trace-address <- parse-trace line:string-address)
     (l:string-address <- get f:trace-address/deref label:offset)