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

[EX Q]: DZfOjrQffR, CXOjrQQc
[EX A]: OjrQ

[EX Q]: ChKUlYUTQQBjZMZkgEed, lmQQBjZMZkgdEf
[EX A]: QQBjZMZkg

[EX Q]: ztwJNkApK, wCPrJNkAulj
[EX A]:
JNkA