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

[EX Q]: YRLHFm, odLHCI
[EX A]: LH

[EX Q]: xzMUdHcoYJFWLOILjrg, vCscoYJFWLzO
[EX A]: coYJFWL

[EX Q]: uQdjNpBJnJJYrM, JBHlgEtdjNpBJnJfLX
[EX A]:
djNpBJnJ