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

Example Input: WTnsmP, INnsIM
Example Output: ns

Example Input: IVnbnqBqdPcXfHotUzCYoaGQy, PAlyypBRRBqdPcXfHotpZs
Example Output: BqdPcXfHot

Example Input: LjLoRzvNVYio, lVXsRzvNZhxg
Example Output:
RzvN