instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
CuizrSvJTRWZK, udyrSvJTRZzkS
answer:
rSvJTR


question:
ZRjPgqbLL, uIsmPgqbBB
answer:
Pgqb


question:
RdeLkqBEKxwB, YkBBakqBEKDh
answer:

kqBEK