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

[Q]: HXYkGv, GCYksu
[A]: Yk


[Q]: yPODMimvyQPYWHfcM, aZiotMimvyQPZncH
[A]: MimvyQP


[Q]: RcXLokQVmlSC, pALokQVmHs
[A]:
LokQVm