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

Example Input: SUgXyznbUQRpiLUTlRb, jlnwLTnbUQRpioUFyJ
Example Output: nbUQRpi

Example Input: CxosNa, ikosdx
Example Output: os

Example Input: ysjbEQFN, imjbEfM
Example Output:
jbE