An integer M (1 ≤ M ≤ 10^9), representing the start of an interval.
An integer N such that (M ≤ N ≤ 10^9), representing the end of an interval. You can assume that (0 ≤ N - M < 1,000,000).

### Example Input:

```
1 9
```

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