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

RMurrwPjlfG, QBKrrwPDkTM
rrwP

jXbgnl, lUbglP
bg

QAvXONsgTUwaN, hzOuHqXONsgTUryQarv

XONsgTU