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

Example Input: STvKOHq, XMGvKOdyM
Example Output: vKO

Example Input: aIZIsqL, wxSZIsEnO
Example Output: ZIs

Example Input: gaVgOGBvvPSHxbZBcBYLFo, zqRwVBvvPSHxbZCfxX
Example Output:
BvvPSHxbZ