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

[EX Q]: jXbgnl, lUbglP
[EX A]: bg

[EX Q]: mJoHBJehHtkFS, ZMrDxHBJehHtxS
[EX A]: HBJehHt

[EX Q]: IPBfHrYDNxWmOe, mwiNTfHrYDNxWrEevZhX
[EX A]:
fHrYDNxW