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: vISTrmBMpQyanUTSXUCm, dJGyOHMpQyanUTpSb
Example Output: MpQyanUT

Example Input: lFDxpJlhL, iiDxpJlZj
Example Output:
DxpJl