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

ICizmXnKMpUH, oDrnmXnKgWXX
mXnK

eeoJEtGHPDvHck, ezPGHPDvHSf
GHPDvH

FWiTkPNSueulmnQ, OkVKTkPNSuLLYIeU

TkPNSu