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

Example Input: PQCjJwXurLeN, vsjJwXuOy
Example Output: jJwXu

Example Input: YCAyruPTTHWhCYaiXfIl, OETdzqAyruPTTHWgS
Example Output: AyruPTTHW

Example Input: kafqealoHroDdYv, nFJLPdqealoHrSoGx
Example Output:
qealoHr