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

Example Input: txJhzNeBj, qLJhzNesV
Example Output: JhzNe

Example Input: XWKEpwGRkfCFZGOyZQOoypx, lhQkmVqeRkfCFZGOyugPLqs
Example Output: RkfCFZGOy

Example Input: yUJdsOlNFnQJCPot, QDdsOlNFnQdhNd
Example Output:
dsOlNFnQ