Please solve the programming task below using a self-contained code snippet in a markdown code block.

Given a string s, return the number of palindromic substrings in it.
A string is a palindrome when it reads the same backward as forward.
A substring is a contiguous sequence of characters within the string.
 
Please complete the following python code precisely:
```python
class Solution:
    def countSubstrings(self, s: str) -> int:
```