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

nhGinCtvLartcMPhJwGRbpZNrq, iQJlFKayEartcMPhJwDRROB
artcMPhJw

jkGcUm, dxGcSI
Gc

HdgXAqjvwP, TlsgXAqjiH

gXAqj