diff --git a/2021/d01/ex1/ex1.py b/2021/d01/ex1/ex1.py
index b9c93da..24cc5d1 100755
--- a/2021/d01/ex1/ex1.py
+++ b/2021/d01/ex1/ex1.py
@@ -6,7 +6,7 @@ from typing import List
 
 
 def solve(input: List[int]) -> int:
-    return sum(prev < cur for (prev, cur) in itertools.pairwise(input))
+    return sum(prev < cur for (prev, cur) in zip(input, input[1:]))
 
 
 def main() -> None: