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

Example Input: sCMyALRSDknURKqZDlqFf, oEIfHyALRSDknUrnMebev
Example Output: yALRSDknU

Example Input: TizkNtJUPHfhmGQ, enzehVkNtJUPHunpG
Example Output: kNtJUPH

Example Input: YcgVJVACcQE, JsJVACcSz
Example Output:
JVACc