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

Example Input: HorIyjpfBFmKZQUIEoP, AcWOaOgVPmyjpfBFmKZQPFYiI
Example Output: yjpfBFmKZQ

Example Input: VpJvIZdkzKovjc, BZEizZdkzKYZ
Example Output: ZdkzK

Example Input: rGNngud, jVNngoIm
Example Output:
Nng