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

[EX Q]: krnkpodgfpCKtfCqyzUbymWbxi, DydgSWpCKtfCqyzDaMsjqc
[EX A]: pCKtfCqyz

[EX Q]: faHRBWyXsYzYmHQyy, aHTyXsYzYeXBFV
[EX A]: yXsYzY

[EX Q]: thdrWyApkCtcThoDb, JTyApkCtcTbT
[EX A]:
yApkCtcT