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

Ex Input:
CiElmOvTqJGVJkfSaDRzE, EjDJwMyxTvTqJGVJkfluB

Ex Output:
vTqJGVJkf

Ex Input:
KKrCLvJKRoyV, WDeLvJKCBdS

Ex Output:
LvJK

Ex Input:
WvXAnQiZpihZsVnrqukak, GgsaHMlOLnQiZpihZsDnDQsMPWB

Ex Output:
nQiZpihZs