instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
xMxyohPBlJIEBqghiMdBQPwq, xsBlJIEBqghlMosK
answer:
BlJIEBqgh


question:
oCtWZYdkvZ, pkktWZYdEHMW
answer:
tWZYd


question:
ypCvaXWTX, ehJvaXFSn
answer:

vaX