instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
zeuyZKwvIOfx, BlmZKwvspUt
answer:
ZKwv


question:
LudFxiaqbX, UWMPnFxiaqikiDx
answer:
Fxiaq


question:
cciThkCShxPDYmCg, jyejVCShxPDYlgu
answer:

CShxPDY