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

[EX Q]: qMnjlfIsQRtUlPggCpHqu, gfVndMwYDIsQRtUlPgqBJKCX
[EX A]: IsQRtUlPg

[EX Q]: OVZxWYzAAxG, rStOxWYzJeoC
[EX A]: xWYz

[EX Q]: SXWYqKeOTpShtGnK, VqLajTqKeOTpShtxSyXMlXjc
[EX A]:
qKeOTpSht