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

Example Input: OyXwTWbLByC, yODnTWbLWYzc
Example Output: TWbL

Example Input: uDaqoOpUtLDdTGTO, ncIgBjDPqoOpUtLDdTNtiEyarDO
Example Output: qoOpUtLDdT

Example Input: GwuKYrXzYtfOlVRoGPwELo, oUueHrKYtfOlVRojxCWK
Example Output:
YtfOlVRo