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

Example Input: RtAchtNymcswVk, FWRuRchtNymcswUkoERHyML
Example Output: chtNymcsw

Example Input: vMsEJRoLkWcmkuwNRz, ZmoLkWcmVZiBv
Example Output: oLkWcm

Example Input: GtJDQoiekEx, TgTQoieBK
Example Output:
Qoie