instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
QvtDqzQiSknPbRCG, hVxHdqzQiSknPbumdpNIf
answer:
qzQiSknPb


question:
HSsyZzZLZAAq, MFEZzZLJC
answer:
ZzZL


question:
VjKGmbFBElT, wwtKGmbFBflQ
answer:

KGmbFB