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]: MSzHyOuaJILkeY, eUibEHoHyOuaJIhfvXy
[EX A]: HyOuaJI

[EX Q]: xhRUqXkpNzt, fmQUqXkGWA
[EX A]:
UqXk