What the h..?
How dow think that way?

As a guess, I'd say 32 is the smallest power of 2 that is large enough for either of the answers.

Some people like to keep everything in powers of 2 (so your code would have s[128] instead) for "efficiency".

I always assumed 0 is positive.
Turns out my assumption is wrong: 0 is neither positive nor negative ( https://mathworld.wolfram.com/Zero.html ).

Maybe add this little piece of information to the problem description?
Thanks!

/ can be symmetric or floored (implementation defined).
The clever code will not work in implementations where division is symmetric.