instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
YRLHFm, odLHCI
answer:
LH


question:
zBNTHKtofMdHfBgJhOfojzM, VIkVdFapofMdHfBgjPCUo
answer:
ofMdHfBg


question:
IfddTKlE, sXMddTVy
answer:

ddT