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

Example Input: VByrCcgcxCfPGDFqIWGloQZTMQf, OqfPGDFqIWGlalTCCkKkMf
Example Output: fPGDFqIWGl

Example Input: tyVlHfTPLRSdFilXnSfqQ, bkTPLRSdFiMgXC
Example Output: TPLRSdFi

Example Input: CzkPtkpMTDeNZwCPbJJn, HzpMVDeNZwCPbJVOU
Example Output:
DeNZwCPbJ