instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
skZGHS, HsZGge
answer:
ZG


question:
DQBpdnwVDcnCDEWpD, gAtCdnwVDcnCYv
answer:
dnwVDcnC


question:
ipsYnUvyWMDQhvNLzJcU, fAWMDQhvNLznTQItDrmz
answer:

WMDQhvNLz