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

[EX Q]: hUpEbyvEcQ, dHpEbyvEvwsXcN
[EX A]: pEbyvE

[EX Q]: lOedgdw, aoedgpn
[EX A]: edg

[EX Q]: HLtkkRnWkgIdqbQH, dWeFUtkkRnWkgIdZhlQh
[EX A]:
tkkRnWkgId