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

CdRbREFMEDTXnEzgn, zHLEMMEDTXnEPH
MEDTXnE

DUhUbmfLuOFAQann, kwnzfLuOFAErR
fLuOFA

chVpHgHgfqxaAkduQcMHSRQOGb, eApLILsjLyfqxaAkduQcERWk

fqxaAkduQc