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

Example Input: oWwqraAz, uxTqraonu
Example Output: qra

Example Input: ZKMRTxCxbsbX, iovHrMRTxCxbsjv
Example Output: MRTxCxbs

Example Input: oshtaTmIKrMUkioqwArpzOVZ, rtmIKrMUkioNAWqSnVZ
Example Output:
mIKrMUkio