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

Example Input: yITbYie, TlqTbYomH
Example Output: TbY

Example Input: GBTHKtWUzK, ovVNKtWUmVJF
Example Output: KtWU

Example Input: DuOSTtCMjS, oAOSTtjqwt
Example Output:
OSTt