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

Example Input: lsNwypFwhKP, diEfLwypFwEKqCN
Example Output: wypFw

Example Input: NTINFnRckGsfLqhSoA, UUONcKKFnRckGsfLqVak
Example Output: FnRckGsfLq

Example Input: ijokGCrdF, MGXkGCVRf
Example Output:
kGC

