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

[EX Q]: spGRUmIYuGl, qkqRUmItqU
[EX A]: RUmI

[EX Q]: zzEhnt, sYEhtc
[EX A]: Eh

[EX Q]: JeGzIe, JrGzVI
[EX A]:
Gz