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

[EX Q]: iYSNsY, HSSNhP
[EX A]: SN

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

[EX Q]: rcKVmDzwJKeK, uYqmDzwJKxkGi
[EX A]:
mDzwJK