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

[EX Q]: PQSFjlnU, kTSFjMUh
[EX A]: SFj

[EX Q]: WlqGjLNrxXeUrKCZel, pDSsmNrxXeUrKCslBXBbRu
[EX A]: NrxXeUrKC

[EX Q]: cyCsTPpHxQcciaOr, xpPepHxQccGw
[EX A]:
pHxQcc