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

ChKUlYUTQQBjZMZkgEed, lmQQBjZMZkgdEf
QQBjZMZkg

RMurrwPjlfG, QBKrrwPDkTM
rrwP

cOiaQPYpVyZX, umZiaQPYdJC

iaQPY