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

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

[EX Q]: kWTQrtCaoTbXIiXDphMG, pLhxkfeDoTbXIiXDpCCzTYyZv
[EX A]: oTbXIiXDp

[EX Q]: YfAqHi, guAqrV
[EX A]:
Aq