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

Example Input: KKebLWQCQzVIojj, nxQCQzVIopD
Example Output: QCQzVIo

Example Input: DZfOjrQffR, CXOjrQQc
Example Output: OjrQ

Example Input: ScrDSefXSziojJRj, qZRSefXSziBXlJTCI
Example Output:
SefXSzi