お題
2つの区間の共通部分を出力せよ

[1,3] [2,4] => [2,3]
(1,2) [1,2] => (1,2)
[0,100) (5,+inf) => (5,100)
(-inf,2] [1,+inf) => [1,2]
[1,2) [2,3) => {}