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

Example Input: XmiLktrUjJDOCJ, UIKrUjJDOQsR
Example Output: rUjJDO

Example Input: RpaZAvSnEBgGapIPQgw, wcwYsXvSnEBgGapIwoIWROB
Example Output: vSnEBgGapI

Example Input: mjCEUoPmeKbvCgUtUL, SrHtrPmeKbvYpQAVp
Example Output:
PmeKbv