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

Example Input: UIjAMFDuxDDGkfQa, VdsHuxDDGkfZHZZ
Example Output: uxDDGkf

Example Input: fAsWQxuyBevvLogrSrgg, tmdBEUxuyBevvLogXjiMCbh
Example Output: xuyBevvLog

Example Input: phUJvGBIttauU, wxPniJvGBItOFcjyL
Example Output:
JvGBIt