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

ZhHtTXaUmsQfUMNrnt, KvvebSXaUmsQfBspwM
XaUmsQf

sbQJFbUtmnKaEJePFPeRM, QzfvkdZbUtmnKaEJNrWD
bUtmnKaEJ

XtxhTGaZEtbU, RlIwTGaZEtSDaQ

TGaZEt