diff --git a/chapter4/SlidingPuzzle.hs b/chapter4/SlidingPuzzle.hs
index ce15ed9..7a59e70 100644
--- a/chapter4/SlidingPuzzle.hs
+++ b/chapter4/SlidingPuzzle.hs
@@ -1,7 +1,8 @@
-module SlidingPuzzle where
 -- Solves the sliding puzzle problem (http://en.wikipedia.org/wiki/Sliding_puzzle)
 -- using A* algorithm
 
+module SlidingPuzzle where
+
 import Data.Ix
 import qualified Data.Array as A
 import Data.Array (Array, array, (//), (!))