An integer N (1 ≤ N ≤ 10000), representing some quantity or size.
An integer K (1 ≤ K ≤ 10000), representing another quantity or size.
An integer X (1 ≤ X ≤ 10000), representing a cost or value.
An integer Y (1 ≤ Y < X ≤ 10000), representing another cost or value.

### Example Input:

```
15
3
10000
9000
```

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