instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
cvZfWOwa, xOfWOhZs
answer:
fWO


question:
KKrCLvJKRoyV, WDeLvJKCBdS
answer:
LvJK


question:
xVtYdWBcjypEotovxvtnbWmXEtJm, HGEPjypEotovxvSVmAj
answer:

jypEotovxv