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

Example Input: CCzKRbuEAmN, qTLzKRbuhEqq
Example Output: zKRbu

Example Input: MriFNpGM, yaiFNduk
Example Output: iFN

Example Input: ufzpSysWeADYYb, ZaSysWeSbd
Example Output:
SysWe