instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
YcgVJVACcQE, JsJVACcSz
answer:
JVACc


question:
yQCDWefwvrPP, RwoMDWefwhSxTR
answer:
DWefw


question:
QEcukWNbQbWRZmAg, KeECmWocukWNbQbWAaiLO
answer:

cukWNbQbW