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

GBTHKtWUzK, ovVNKtWUmVJF
KtWU

HqaOvLaZbs, RifOvLaZkh
OvLaZ

kbVBbZBEk, buBbZgNw

BbZ