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

Example Input: bjjsMtBzzXIgYWPBZmaDL, iTxktmvBzzXIgYWPhbAyBE
Example Output: BzzXIgYWP

Example Input: haOsaSQcyodWhqQaC, BKLEUQcyodWhvVkmxBz
Example Output: QcyodWh

Example Input: AUEJKoigchPzeh, bvaNAKoigcRubR
Example Output:
Koigc