instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
gwVLygvd, VOQLyglfo
answer:
Lyg


question:
cKsJcqYvZO, UrsJcqBC
answer:
sJcq


question:
IyfSop, gDfSVZ
answer:

fS