instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
RtAchtNymcswVk, FWRuRchtNymcswUkoERHyML
answer:
chtNymcsw


question:
lkFGXvTkKm, wwELXvTkcOnG
answer:
XvTk


question:
nioxdobaXUJWh, AsfpwMdobaXUYNXN
answer:

dobaXU