An integer n (1 ≤ n ≤ 100000), representing some quantity or size.
A list of integers a of size n, where each integer is between 1 and 100000.

### Example Input:

```
7
3 1 4 1 5 9 2
```

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