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

Example Input: iMwanJBuMdiZDL, kIafHeBuMdiZmKNA
Example Output: BuMdiZ

Example Input: wrVsKN, mOVsWo
Example Output: Vs

Example Input: prrCvhyOiiqTJdyxCF, uysvIlvyOiiqTJdyxwnx
Example Output:
yOiiqTJdyx