instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
QlJnxO, BLJnCQ
answer:
Jn


question:
TnbLNKnNSs, NhDLNKnNRd
answer:
LNKnN


question:
HZaLCaPIDZnOPLIPlGIXhPMM, ljayYoWqDZnOPLIPyh
answer:

DZnOPLIP