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

IGHhMfqLeBpnullsPInfBH, LTDBpnullsPIBynwCrCQ
BpnullsPI

bUcuzFgsdfojVR, IdcuzFgsdMRgtMA
cuzFgsd

HfOYySgdBWMqhQUQ, qUmgdBWMqhFo

gdBWMqh