Let's tackle the day 4 challenge!

In this one, we get an input like this:

2-4,6-8
2-3,4-5
5-7,7-9
2-8,3-7
6-6,4-6
2-6,4-8

Each line has two ranges: the first line has ranges containing 2, 3, 4, and 6, 7, 8. We must count how many pairs have ranges where one fully contains the other.

In Rust, we can express this with "inclusive ranges" (), and those implement , so we can do: