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

[EX Q]: bjjsMtBzzXIgYWPBZmaDL, iTxktmvBzzXIgYWPhbAyBE
[EX A]: BzzXIgYWP

[EX Q]: QEEVsnbQIgrxaZmflaZ, dPSbljkdQIgrxaZmgVzMT
[EX A]: QIgrxaZm

[EX Q]: QAQRvo, ZtQRWc
[EX A]:
QR