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

Example Input: koddLvYmRXDUuUnW, GnqDYGmmRXDUuUquAnf
Example Output: mRXDUuU

Example Input: iMwanJBuMdiZDL, kIafHeBuMdiZmKNA
Example Output: BuMdiZ

Example Input: kQnNnfYJ, wutnNnQjp
Example Output:
nNn