instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
jinzsW, SMnzaW
answer:
nz


question:
yPODMimvyQPYWHfcM, aZiotMimvyQPZncH
answer:
MimvyQP


question:
HKCoXQsLRtowYJ, PGRzNUQsLRtoLcqkn
answer:

QsLRto