instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
zBNTHKtofMdHfBgJhOfojzM, VIkVdFapofMdHfBgjPCUo
answer:
ofMdHfBg


question:
LudFxiaqbX, UWMPnFxiaqikiDx
answer:
Fxiaq


question:
OGHuXKJodoDxBTmcIkPnJDHQu, SjCyoDxBTmcIkPOYl
answer:

oDxBTmcIkP