Update README.md

Author: SaykoMe

README.md

@@ -225,4 +225,5 @@ This project is licensed under the MIT License - see the [LICENSE](LICENSE) file
 - [Find the Duplicate Number](Python/find_the_duplicate_number.py)
 - [Buy Two Chocolates](Python/buy_two_chocolates.py)
 - [First Missing Positive](Python/first_missing_positive.py)
-- [Subarray Product Less Than K](Python/subarray_product_less_than_k.py)
+- [Subarray Product Less Than K](Python/subarray_product_less_than_k.py)
+- [Valid Parentheses](Python/valid_parentheses.py)