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

Example Input: BfCCzPNLBbwCoxMVAG, vhwNLBbwCbH
Example Output: NLBbwC

Example Input: wDSKHtWbCDqTeoBeiYHdcZD, MydQCwqTeoBeiYHdYMp
Example Output: qTeoBeiYHd

Example Input: fEcbrYeeIwdK, junbrYeeIqGVEI
Example Output:
brYeeI