and how long?)

So tests actually don't pass. See https://docs.codewars.com/training/troubleshooting/.

I've now added the note, and the puzzle tag.

I still think the puzzle tag is a bad idea, since it will make people think there is trickery going on (when there really isn't), or that they have to break open weigh or something (which they don't), but enough people have asked for it, so there it is.

(I'd leave the note aside and add the pussle tag instead, but as you prefere)

... Ok I can add that, but what other katas have notes telling you which approaches are the "wrong" ones? Usually finding the right approach is part of the challenge of the kata.

Anyway I'll add a note.

I disagree about the "puzzle" tag. Just because it involves some math doesn't automatically make it a puzzle kata. A puzzle kata is when the user doesn't have all the information, and has to figure out what the expected return value is, or some other information.

In this kata, all the information is available, nothing is hidden. It requires clever thinking, but that alone doesn't make it a puzzle, otherwise almost every hard kata would be a 'puzzle'.

It isn't impossible (and there are quite some measures to prevent reflection etc). Maybe think about why the description talks about boxes full of ball bearings, and not just directly talking about comparing single items.