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

[EX Q]: vhZuXCsIkQR, YflCuXCsIkLu
[EX A]: uXCsIk

[EX Q]: CiElmOvTqJGVJkfSaDRzE, EjDJwMyxTvTqJGVJkfluB
[EX A]: vTqJGVJkf

[EX Q]: ftvxfhsnJEygzV, JYxSfhsnJnIqkW
[EX A]:
fhsnJ