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: yRhCObvPZYoKUoQnyaatR, NHzLJYPZYoKUoQnJnIsZxC
Example Output: PZYoKUoQn

Example Input: VQoIHPrxKrujsjKg, sBjHNoIHPrxKrOcw
Example Output:
oIHPrxKr