Solve the programming task below in a Python markdown code block.
---

# Story

The Pied Piper has been enlisted to play his magical tune and coax all the rats out of town.

But some of the rats are deaf and are going the wrong way!

# Kata Task

How many deaf rats are there?

# Legend

* ```P``` = The Pied Piper
* ```O~``` = Rat going left
* ```~O``` = Rat going right

# Example

* ex1 ```~O~O~O~O P``` has 0 deaf rats


* ex2 ```P O~ O~ ~O O~``` has 1 deaf rat


* ex3 ```~O~O~O~OP~O~OO~``` has 2 deaf rats

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# Series

* [The deaf rats of Hamelin (2D)](https://www.codewars.com/kata/the-deaf-rats-of-hamelin-2d)
Also feel free to reuse/extend the following starter code:
```python
def count_deaf_rats(town):
```