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

Example Input: zzEhnt, sYEhtc
Example Output: Eh

Example Input: XqyPjqNZDEK, EfwPjqNgjIP
Example Output: PjqN

Example Input: BxFVIOxsKbCsdVVXSBNdy, BUXiFVIOxsKbCsbqJcW
Example Output:
FVIOxsKbCs