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

Example Input: qczzCr, zDzzUI
Example Output: zz

Example Input: XMtSwZVAHsNYhbyDm, asAVAHsNYhSPuNLrV
Example Output: VAHsNYh

Example Input: zgZMcQotQpz, mLMcQokE
Example Output:
McQo