As I know, at first, possible errors, non-standard situations are written in the if block.

I agree, although I would never get to the mathematical formula, as I'm not a mathematical person, but there is a massive difference between running the function with a considerably high "m" number
when your solution solves it instantly.

Very interesting the always problematic execution time :)

It's clever, but I think you could exclude the "else" from the statement, since "return" ends the function execution.
It would increase readability.