An integer N (1 ≤ N ≤ 1,000,000), representing some quantity or size.
A string S of length N, consisting of lowercase English letters.
A string T of length N, consisting of lowercase English letters.

### Example Input:

```
5
abcde
aaacc
```

### Function Signature:
Write a function f(N, S, T) that takes in the input.
def f(N: int, S: str, T: str):
    ''' 
    N: an integer 
    S: a string 
    T: a string 
    '''