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

Example Input: KTAFonizDqCVvucpJWrItdw, rfFonizDqCVvYbGhb
Example Output: FonizDqCVv

Example Input: EOacPYivmmUlYenynBqAwx, MoZWMOeXmUlYenynBEendWg
Example Output: mUlYenynB

Example Input: fTSgJvcCvBnckCD, fCobbcCvBnckHKPln
Example Output:
cCvBnck