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]: fBpRXPkikQokGVeS, FwUbKXkikQokGos
[EX A]: kikQokG

[EX Q]: SgNWkvBnRTFVEUeEgRbpfgu, EerrUnRTFVEUeQDyLaM
[EX A]:
nRTFVEUe