instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
sJRFPufsaWXNeu, AePufsafc
answer:
Pufsa


question:
XqyPjqNZDEK, EfwPjqNgjIP
answer:
PjqN


question:
NnyEawPnBwwr, zztawPnBwfA
answer:

awPnBw