An integer N (1 ≤ N ≤ 70), representing some quantity or size.
An integer K (1 ≤ K ≤ 70), representing some quantity or size.
A string s of length K, consisting of characters from the set {'r', 'b'}.

### Example Input:

```
12 2
rb
```

### Function Signature:
Write a function f(N, K, s) that takes in the input. 
def f(N: int, K: int, s: str): 
    ''' 
    N: an integer 
    K: an integer 
    s: a string 
    '''