I was thinking along the same lines as you, but it turns out you only need two comparisons and one logical operator.

barrkel has a thorough explanation here:

https://news.ycombinator.com/item?id=14641485

Or, as I realized later, it seems helpful to me if I look at it as a practical problem instead of an abstract one:

https://news.ycombinator.com/item?id=14642059