fixed a little bug

(Put an X inside the [ ] to denote check mark [X].)

• If creating a new file :

  • added links to it in the README files ?
  • included tests with it ?
  • added description (overview of algorithm, time and space compleixty, and possible edge case) in docstrings ?

• if done some changes :

  • [X ] wrote short description in the PR explaining what the changes do ?
  • Fixes #[issue number] if related to any issue

• other