instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
Owbiay, exbime
answer:
bi


question:
STvKOHq, XMGvKOdyM
answer:
vKO


question:
QojFtSrAgFCi, PcqfAYjFtSrAExf
answer:

jFtSrA