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

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


[Q]: YCAyruPTTHWhCYaiXfIl, OETdzqAyruPTTHWgS
[A]: AyruPTTHW


[Q]: cJiugSfNEU, JBgSfNKabj
[A]:
gSfN