In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.

zBNTHKtofMdHfBgJhOfojzM, VIkVdFapofMdHfBgjPCUo
ofMdHfBg

dxqZUOvRprXyFfjQfTWBhR, biSVjOvRprXyFfDtuFWQ
OvRprXyFf

mUXBXtKhpFSfiMTBE, MnIrddjdOJXBXtKhpFSfNEALM

XBXtKhpFSf