instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
yKtQOhYvrJVH, HQsTQOhYvPP
answer:
QOhYv


question:
UCbReSfuLcbzmBCl, snQRReSfuLcbzmjqVPSdpp
answer:
ReSfuLcbzm


question:
OnYcrS, htYcNb
answer:

Yc