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

Example Input: jdLbZSCzaAHGbNwILGmudOH, RdIPuEYJvUZSCzaAHGbNduLToRC
Example Output: ZSCzaAHGbN

Example Input: yjoJzBGdwfOhsceoOpoap, uSLMdBGdwfOhsIQHBijd
Example Output: BGdwfOhs

Example Input: QLHfDOJoLYpDvTEhxu, MBTRqDOJoLYpxoyKI
Example Output:
DOJoLYp