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

Example Input: haOsaSQcyodWhqQaC, BKLEUQcyodWhvVkmxBz
Example Output: QcyodWh

Example Input: TizkNtJUPHfhmGQ, enzehVkNtJUPHunpG
Example Output: kNtJUPH

Example Input: RYPbfjrf, IuPbfQhM
Example Output:
Pbf