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

Example Input: gHFwDorPbNPORVgdLW, AfqDQvCGFwDorPbNPVPVmbQ
Example Output: FwDorPbNP

Example Input: QqtCFzXHPNFXx, XECFzXHPSGwUuk
Example Output: CFzXHP

Example Input: nDbjJonzsKtoBag, VvNjJonzsKaiqy
Example Output:
jJonzsK