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

[EX Q]: QgkpBHsrfRYJCa, AdjbKLpBHsrfbpBC
[EX A]: pBHsrf

[EX Q]: gTjTwC, OUjTgM
[EX A]: jT

[EX Q]: QvgEquRLwD, AsgEquGot
[EX A]:
gEqu