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

AxRSlkQfWHrdlgQG, iXIOrmlkQfWHTy
lkQfWH

rvLoiycpZw, idcvoiycpcLyD
oiycp

aYhOEBZQZaYJkFJYYVeEkN, dWYJkFJYYVeEUYo

YJkFJYYVeE