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

Example Input: iaXeqfIrYKxPJRXxfSm, rIYKxPJRXxfsjVsqe
Example Output: YKxPJRXxf

Example Input: VeLJEBYpZwxVQlo, EZEBYpZwxVQIxjFj
Example Output: EBYpZwxVQ

Example Input: aJamnxMSIEMeMZEACOIqfEiK, uvIUxWWVzSIEMeMZEAcRljuf
Example Output:
SIEMeMZEA