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

Example Input: dxqZUOvRprXyFfjQfTWBhR, biSVjOvRprXyFfDtuFWQ
Example Output: OvRprXyFf

Example Input: fREVIdeTcakgFnwDWTVev, IbtXImseeTcakgFnwDYsKBAlux
Example Output: eTcakgFnwD

Example Input: uODomfyHPD, KevDmfyHQTiS
Example Output:
mfyH