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

[EX Q]: cZSEmdgP, YsSEmEIM
[EX A]: SEm

[EX Q]: jkGcUm, dxGcSI
[EX A]: Gc

[EX Q]: YIiAebDGeQBOQt, SjiwbDGeQBOOesMfoF
[EX A]:
bDGeQBO