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

[EX Q]: NxgzLSzFGa, JvLzLSzsuj
[EX A]: zLSz

[EX Q]: UCbReSfuLcbzmBCl, snQRReSfuLcbzmjqVPSdpp
[EX A]: ReSfuLcbzm

[EX Q]: DhhYhrqVMXSoyvXQwqPKzWARAP, CaMXSoyvXQwqcDDtMsVqD
[EX A]:
MXSoyvXQwq