diff --git a/chapter3/13_sliding-window-maximum.py b/chapter3/13_sliding-window-maximum.py
index 7ca5187..896247e 100644
--- a/chapter3/13_sliding-window-maximum.py
+++ b/chapter3/13_sliding-window-maximum.py
@@ -31,7 +31,7 @@
 #######################################################################################
 
 import collections
-
+    
 
 class Solution:
     def maxSlidingWindow(self, nums, k):