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

[EX Q]: hVQJkZyKfPoOQEukfAbXDpB, qpojyxWkZyKfPoOQEZkUI
[EX A]: kZyKfPoOQE

[EX Q]: gfDDsblwUryUw, UWaRisblwUTqTM
[EX A]: sblwU

[EX Q]: QCVTteiaNGuKZDxqzpl, PBpirTteiaNGuKZTZnSAh
[EX A]:
TteiaNGuKZ