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

Example Input: jFVaEHbMrrkW, ekfVaEHbPnBnM
Example Output: VaEHb

Example Input: tmBlKUto, eFDBlKLy
Example Output: BlK

Example Input: laAnADQpjCSohvFk, LtnADQpjCrltW
Example Output:
nADQpjC