diff --git a/leap_year.py b/leap_year.py
index 5fdea2b..b7367ca 100755
--- a/leap_year.py
+++ b/leap_year.py
@@ -19,9 +19,9 @@ def get_day_of_month(year, month: int) -> int:
 
 
 def get_day_of_month2(year, month: int) -> int:
-    if [1, 3, 5, 7, 8, 10, 12].__contains__(month):
+    if month in {1, 3, 5, 7, 8, 10, 12}:
         return 31
-    elif [4, 6, 9, 11].__contains__(month):
+    elif month in {4, 6, 9, 11}:
         return 30
     elif month == 2 and is_leap_year(year):
         return 29