An integer n (1 ≤ n ≤ 100), representing some quantity or size.
An integer m (m ≤ n), representing another quantity or size.
A list of m characters, where each character is from the set {'A', 'B', 'C', 'D'}.

### Example Input:

```
5 3
A
B
C
```

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