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

Example Input: IzwlZDJSEFPxfIud, xwWSYwlZDJSEFPbvSXTlS
Example Output: wlZDJSEFP

Example Input: HEVqGddewrNqiZ, iyvlddewrNXr
Example Output: ddewrN

Example Input: EaPdfXHVUdLGdRRtzVJG, WbzWKMvpXHVUdLGdBtviuT
Example Output:
XHVUdLGd