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

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

[EX Q]: ksRxEVrz, cOMRxEViwF
[EX A]: RxEV

[EX Q]: YaTDMuua, TTpTDMNgk
[EX A]:
TDM