An integer N (3 ≤ N ≤ 2047), where N is odd.
A 2D list of characters A of size N x N, where each character is either 'o' or 'x'.

### Example Input:

```
5
oxooo
oxooo
oxooo
xxxxx
oxooo
```

### Function Signature:
Write a function f(N, A) that takes in the input.
def f(N: int, A: List[List[str]]):
    '''
    N: an integer
    A: a 2D list of characters
    '''
