Out of thin air:

> I forget how much time they gave for it. Let’s say three hours, counting the time to explain the problem.

ankrgyl claims to be the author of the question; I don't think they're the author of this blog post about the question.

The blog post is where that duration came from; I think both the asker and the question author missed the first part of the line from it I quoted.

If you search the rest of the comments here for "three hour" there's quite a few people jumping on that rather than just accepting it as "eh, I don't remember so I'll just throw something out there".