If your function type changes in C you'd better rewrite your code however. What if it becomes a string? There is a problem to solve, with specifications, makes no sense to assume if whatever could happen.

I'm thinking of maintaining the code - works for this solution - but not a best practice

Why do you want it to change?

This seems like a bad practice as it relys on being an int, if the function were to change to be a float/double then this wouldn't produce correct answer.