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

[EX Q]: kIBDjQLEZepVNHqnKqhine, hTZepVNHqnYTajyzv
[EX A]: ZepVNHqn

[EX Q]: NwmTIZSnlKGG, qAYIZSnfWRd
[EX A]: IZSn

[EX Q]: sFffEL, vVffXP
[EX A]:
ff

