An open interval is the set of all numbers between a lower and upper bound. In mathematical notation, we write

(a, b) = { x | a < x < b }

Your task is to determine when two intervals *overlap*. For
example, the intervals (1, 3) and (2, 4) overlap, as do (1, 4) and (2, 3).
But the intervals (1, 2) and (3, 4) do not overlap.