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

Example Input: VRamNL, mUamIB
Example Output: am

Example Input: rcKVmDzwJKeK, uYqmDzwJKxkGi
Example Output: mDzwJK

Example Input: iuZIPwig, komZIPJcI
Example Output:
ZIP