instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
wrVsKN, mOVsWo
answer:
Vs


question:
SODsrWUjUBSgA, WIWUjUBCUUs
answer:
WUjUB


question:
xATIQfzDPDaAyXd, JPDSjoIQfzDPDpO
answer:

IQfzDPD