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

Example Input: BVipiZoGXaWdjmDsxWP, yxppsiYkiZoGXaWdjoDRuKW
Example Output: iZoGXaWdj

Example Input: SUgXyznbUQRpiLUTlRb, jlnwLTnbUQRpioUFyJ
Example Output: nbUQRpi

Example Input: vxvYcbOBvUVoCgpToD, kvmFpNaOBvUVoCJSz
Example Output:
OBvUVoC