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

Example Input: uRLpAWCotLmxcSmKyvo, laotLmxcSmKyBwVfJB
Example Output: otLmxcSmKy

Example Input: vISTrmBMpQyanUTSXUCm, dJGyOHMpQyanUTpSb
Example Output: MpQyanUT

Example Input: vaexqYZpBLBvcktU, dMJXGsZpBLBvno
Example Output:
ZpBLBv