[frostmatthew]

> if you pass in a negative number then that's your own dumb fault if it does something unexpected

If a negative number isn't valid input that should be gracefully handled by the program (e.g. by responding with an appropriate error indicating what is valid and/or invalid) instead of doing something unexpected.

I'm not much of a fan of the current state of tech interviews but seeking clarity around validity of input and how to react to invalid input is one aspect that does (or at least should) mimic "real life"