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

Example Input: JjEQVKijeyEQ, dwSVKijeywCTvb
Example Output: VKijey

Example Input: VByrCcgcxCfPGDFqIWGloQZTMQf, OqfPGDFqIWGlalTCCkKkMf
Example Output: fPGDFqIWGl

Example Input: gfKCDPVJiZ, ssTDPVJaJ
Example Output:
DPVJ