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

[EX Q]: iJbjApY, ggwbjAws
[EX A]: bjA

[EX Q]: faHRBWyXsYzYmHQyy, aHTyXsYzYeXBFV
[EX A]: yXsYzY

[EX Q]: rgeQiQeMfDrWa, CtTQeMfDKRK
[EX A]:
QeMfD