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

[EX Q]: sHndIbPaygfNvnquxIHeteW, huLmJWXZIgfNvnquxIViQDhbuoL
[EX A]: gfNvnquxI

[EX Q]: IGHhMfqLeBpnullsPInfBH, LTDBpnullsPIBynwCrCQ
[EX A]: BpnullsPI

[EX Q]: UWsHTXbnBFsbMKuUTRvbJSrt, aKaAGQjNvbnBFsbMKuQeVaqr
[EX A]:
bnBFsbMKu

