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

QgkpBHsrfRYJCa, AdjbKLpBHsrfbpBC
pBHsrf

fREVIdeTcakgFnwDWTVev, IbtXImseeTcakgFnwDYsKBAlux
eTcakgFnwD

QEEVsnbQIgrxaZmflaZ, dPSbljkdQIgrxaZmgVzMT

QIgrxaZm