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

[EX Q]: NxgzLSzFGa, JvLzLSzsuj
[EX A]: zLSz

[EX Q]: nFgMXUzpStDAybiwm, aNJrXUzpStDjp
[EX A]: XUzpStD

[EX Q]: cFHZNYqlN, BISZNYqTEdy
[EX A]:
ZNYq