diff --git a/04-giant-squid/code.scm b/04-giant-squid/code.scm
index c634f95..9216af8 100644
--- a/04-giant-squid/code.scm
+++ b/04-giant-squid/code.scm
@@ -1,14 +1,6 @@
 (import (srfi :43))
 
-; returns a list of numbers parsed from the first line of the file,
-; separated by commas
-(define (parse-draws file)
-  (let loop [(draws '()) (n 0)]
-    (let [(c (get-char file))]
-      (cond
-	[(char=? c #\,) (loop (cons n draws) 0)]
-	[(char-whitespace? c) (reverse (cons n draws))]
-	[else (loop draws (+ (* n 10) (string->number (string c))))]))))
+(load "../common.scm")
 
 ; returns numbers 0 to 9 from ascii character
 (define (char->number c)
@@ -140,7 +132,7 @@
 (call-with-input-file
   "input"
   (lambda (file)
-    (let* [(draws (parse-draws file))
+    (let* [(draws (read-comma-separated-numbers file))
 	   (boards (read-boards file))]
       (printf "part 1: ~% ")
       (let* [(marks (make-vector (length boards) 0))
diff --git a/06-lanterfish/code.scm b/06-lanterfish/code.scm
index 54b1687..ffe2cd0 100644
--- a/06-lanterfish/code.scm
+++ b/06-lanterfish/code.scm
@@ -1,14 +1,5 @@
 (import (srfi :43)) ; vector extensions
-
-; returns a list of numbers parsed from the first line of the file,
-; separated by commas
-(define (read-comma-separated-numbers file)
-  (let loop [(draws '()) (n 0)]
-    (let [(c (get-char file))]
-      (cond
-	[(char=? c #\,) (loop (cons n draws) 0)]
-	[(char-whitespace? c) (reverse (cons n draws))]
-	[else (loop draws (+ (* n 10) (string->number (string c))))]))))
+(load "../common.scm")
 
 ;; naive version, as per the example
 ; simulate lanterfish growth and returns the number of fishes after given days
diff --git a/common.scm b/common.scm
new file mode 100644
index 0000000..e839719
--- /dev/null
+++ b/common.scm
@@ -0,0 +1,9 @@
+; returns a list of numbers parsed from the first line of the file,
+; separated by commas
+(define (read-comma-separated-numbers file)
+  (let loop [(draws '()) (n 0)]
+    (let [(c (get-char file))]
+      (cond
+	[(char=? c #\,) (loop (cons n draws) 0)]
+	[(char-whitespace? c) (reverse (cons n draws))]
+	[else (loop draws (+ (* n 10) (string->number (string c))))]))))