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

Example Input: uRLpAWCotLmxcSmKyvo, laotLmxcSmKyBwVfJB
Example Output: otLmxcSmKy

Example Input: cvZfWOwa, xOfWOhZs
Example Output: fWO

Example Input: GwkzDkcuTzkOmySFtFJXiYnD, CrXShkWCIkcuTzkOmySbEnbJIhrUd
Example Output:
kcuTzkOmyS