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

[Q]: EPUxsZtt, KgxsZuXM
[A]: xsZ


[Q]: rqhQxQQDdYwemFiiwcfVx, cEQDdYwemFtwpfNJC
[A]: QDdYwemF


[Q]: UegKPJpNuJlQo, MYwYYKPJpNwdjy
[A]:
KPJpN