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

HXYkGv, GCYksu
Yk

BfCCzPNLBbwCoxMVAG, vhwNLBbwCbH
NLBbwC

pJauabzVwYtoo, lXqJIuabzVwYtYpoz

uabzVwYt