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

[EX Q]: WTnsmP, INnsIM
[EX A]: ns

[EX Q]: dmigbcBoWdAIyaeE, zXiKQFbcBoWdAIyaEypIjJpwbU
[EX A]: bcBoWdAIya

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