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

Example Input: xzMUdHcoYJFWLOILjrg, vCscoYJFWLzO
Example Output: coYJFWL

Example Input: yQRDycTycwH, ImycTycrR
Example Output: ycTyc

Example Input: yxJxNRLEnKGHziJtfb, KfReWhEnKGHzitzfPWzK
Example Output:
EnKGHzi