instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
mOGzbnDXWnNurkBXtcqZ, NLahGzbnDXWnNYgMTOR
answer:
GzbnDXWnN


question:
slTUxy, oqTUYa
answer:
TU


question:
yQCDWefwvrPP, RwoMDWefwhSxTR
answer:

DWefw