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

Example Input: ilgSzrcUKLTNLJbMKMKSt, hFXIuUKLTNLJbMKWxSCkDjY
Example Output: UKLTNLJbMK

Example Input: nuwMzarLqoPvabJla, JKcrLqoPvabJNDCILGQ
Example Output: rLqoPvabJ

Example Input: OHLSxbuivpCQpC, SObuivpkuKC
Example Output:
buivp