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

Example Input: CCzKRbuEAmN, qTLzKRbuhEqq
Example Output: zKRbu

Example Input: YCAyruPTTHWhCYaiXfIl, OETdzqAyruPTTHWgS
Example Output: AyruPTTHW

Example Input: TyorllbtkaoGoAx, ihwVHorllbtkaDdDe
Example Output:
orllbtka