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

[EX Q]: FQAznAuFjoBKRKB, hPmtFFPnuAznAuFjoBKTgkeJyjcd
[EX A]: AznAuFjoBK

[EX Q]: nXVXIEGP, fkXIEkU
[EX A]: XIE

[EX Q]: jjYkVnhDJgBvfsBiluTJc, ZGenhDJgBvfsnxTLTpoDc
[EX A]:
nhDJgBvfs