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

Example Input: fdinRdwwlntwqzYGhV, ZefonRdwwlntoWQbh
Example Output: nRdwwlnt

Example Input: UtUSmsOI, dCUSmGoQ
Example Output: USm

Example Input: rMyfoRfzuaySFTLztbf, HXeNeyfoRfzuaydWtBMiv
Example Output:
yfoRfzuay