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

ZGkBNEDRAwURXnxBIOJkzTvg, HMAwURXnxBMfGbPOBf
AwURXnxB

XwBMFIV, SNLBMFZQ
BMF

nnomSBycVNfxbW, NTTvomSBycVNXbgPs

omSBycVN