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

Example Input: TdvkBvVyJcSdYGGPfnyml, rIvIvVyJcSdYhtxG
Example Output: vVyJcSdY

Example Input: RNYHvcNnbsUdJLvS, PpNnbsUdglWhl
Example Output: NnbsUd

Example Input: GgFYGLutqlkH, AHWxbFYGLutqltAlEnX
Example Output:
FYGLutql