An integer N (3 ≤ N ≤ 2047), representing some dimension. N is odd.
A list of N strings where each string is of length N, and each character in the string is either 'o' or 'x'.

### Example Input:

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

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