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

bmsrkXGb, GcarkXOZF
rkX

mJoHBJehHtkFS, ZMrDxHBJehHtxS
HBJehHt

OJWBXiUYkHpi, dMpXiUYkHoO

XiUYkH