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

Example Input: cCDTMXjGMNikONun, jpcMXjGMNizBEWQzT
Example Output: MXjGMNi

Example Input: fREVIdeTcakgFnwDWTVev, IbtXImseeTcakgFnwDYsKBAlux
Example Output: eTcakgFnwD

Example Input: sGiiEeAaUaMHXyBvS, pUpjiiEeAaUaXGWQnB
Example Output:
iiEeAaUa