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

Example Input: hcmMoVBhK, mdmMoVBjuT
Example Output: mMoVB

Example Input: ChKUlYUTQQBjZMZkgEed, lmQQBjZMZkgdEf
Example Output: QQBjZMZkg

Example Input: RxXUnkEeSvs, PXNAiXUnkEqm
Example Output:
XUnkE