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

[EX Q]: OyrqfQQnzOFUzrkDM, iBkQQnzOFewhjvO
[EX A]: QQnzOF

[EX Q]: jdLbZSCzaAHGbNwILGmudOH, RdIPuEYJvUZSCzaAHGbNduLToRC
[EX A]: ZSCzaAHGbN

[EX Q]: AKsLDBKnT, EqxsLDBIzG
[EX A]:
sLDB