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

[EX Q]: jkGcUm, dxGcSI
[EX A]: Gc

[EX Q]: BpGFyhLez, DfFyhuJY
[EX A]: Fyh

[EX Q]: HorIyjpfBFmKZQUIEoP, AcWOaOgVPmyjpfBFmKZQPFYiI
[EX A]:
yjpfBFmKZQ