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

Example Input: iupYjFXrrMqWzJSLUSwmEukHc, hqajjWrrMqWzJSLnF
Example Output: rrMqWzJSL

Example Input: hVQJkZyKfPoOQEukfAbXDpB, qpojyxWkZyKfPoOQEZkUI
Example Output: kZyKfPoOQE

Example Input: XqsXJbaeqfCmsTH, RDWJbaeqfChzcTZVm
Example Output:
JbaeqfC