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

[EX Q]: rszjOPpbXm, pnBujOPpWHz
[EX A]: jOPp

[EX Q]: RwqzMTeLMdPx, qaWtYhqzMTeLMdHbWDT
[EX A]: qzMTeLMd

[EX Q]: jQVHEFDJGxFfpEPnxyS, feKXmJGxFfpEfbl
[EX A]:
JGxFfpE