diff --git a/gradation.py b/gradation.py
old mode 100644
new mode 100755
index 6b90c1e..a4e59a7
--- a/gradation.py
+++ b/gradation.py
@@ -1,3 +1,4 @@
+#!/bin/env python3
 
 from __future__ import annotations
 from typing import Union