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

Example Input: xQcYRVFFqrVAMsBm, VErcKZvcYRVFFqzKo
Example Output: cYRVFFq

Example Input: VByrCcgcxCfPGDFqIWGloQZTMQf, OqfPGDFqIWGlalTCCkKkMf
Example Output: fPGDFqIWGl

Example Input: LToWegOvqyhrvqNmzINc, HAcwHvkUvHWegOvqyhrvRudzoK
Example Output:
WegOvqyhrv