In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.

[EX Q]: xeKSiBafhOWBbYwlGaQ, GUfIsKgafhOWBbYiFWnptAt
[EX A]: afhOWBbY

[EX Q]: BUvWkxrAvDQG, rHrkxrAkCE
[EX A]: kxrA

[EX Q]: aANDVqtpI, BKaDVqvUo
[EX A]:
DVq