instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
GrvtMjEvRlmN, ifGOWMjEvRPSOZK
answer:
MjEvR


question:
BmwpAnWJ, klVwpAFw
answer:
wpA


question:
ekzvfgFkOLxtOk, McgtFhiKzvfgFkOLrBTZZw
answer:

zvfgFkOL