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

[Q]: rCFrfkmXbSHK, mztfkmXwez
[A]: fkmX


[Q]: lLxXqKscqizXTO, TqrKscqizutDudo
[A]: Kscqiz


[Q]: oTNfSyDfSpbMqe, krNfSyDfokRgca
[A]:
NfSyDf