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

[EX Q]: nhGinCtvLartcMPhJwGRbpZNrq, iQJlFKayEartcMPhJwDRROB
[EX A]: artcMPhJw

[EX Q]: RAmKlEAUfWcgF, ZlWfEAUfWvVRa
[EX A]: EAUfW

[EX Q]: nDvawkfAVvtTj, ePawkfAVHOKCQD
[EX A]:
awkfAV