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

Example Input: fVEFJa, WtEFYK
Example Output: EF

Example Input: ScUCglVzZFPjLVofNHOumU, mNodEXwpZFPjLVofYfSnBM
Example Output: ZFPjLVof

Example Input: pMtGahgtFRLZExVHwEUjARQYOh, egRLZExVHwEUhP
Example Output:
RLZExVHwEU