instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
koIZvrJmfKCO, TBvrtjcWIZvrJmfKRZDOE
answer:
IZvrJmfK


question:
lOedgdw, aoedgpn
answer:
edg


question:
iUtNuU, iKtNWk
answer:

tN