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

Example Input: XjYkMfARxWBSBjuXyDrFt, EtUxIfiHkMfARxWBSckTLTTnR
Example Output: kMfARxWBS

Example Input: DFRoMPNDAzNgtLsEPseOzC, qykyPjDAzNgtLsEPYTsNrJaNK
Example Output: DAzNgtLsEP

Example Input: NQlqhAelrM, zGNFVKlqhAelManYb
Example Output:
lqhAel