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

[EX Q]: vMsEJRoLkWcmkuwNRz, ZmoLkWcmVZiBv
[EX A]: oLkWcm

[EX Q]: gHFwDorPbNPORVgdLW, AfqDQvCGFwDorPbNPVPVmbQ
[EX A]: FwDorPbNP

[EX Q]: vrFOpJ, VvFOYI
[EX A]:
FO