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

RMurrwPjlfG, QBKrrwPDkTM
rrwP

cvRdSsuNwGVEwSSrowDpaOu, gFMcLKIeLwNwGVEwSSroUGskaoloqC
NwGVEwSSro

QbXZzHbQOkusPrJp, KwXZzHbQOjY

XZzHbQO