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

[EX Q]: HKCoXQsLRtowYJ, PGRzNUQsLRtoLcqkn
[EX A]: QsLRto

[EX Q]: spUbdWDLWCeqr, vIuHkWDLWCQEPaz
[EX A]: WDLWC

[EX Q]: NYFtadDZG, lKiEtadDwd
[EX A]:
tadD