instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
ZRjPgqbLL, uIsmPgqbBB
answer:
Pgqb


question:
ahPbomjSH, rBbomynK
answer:
bom


question:
XWUKZmBJeavuuVtLkizIV, GNavuuVtLkizxFjfZQ
answer:

avuuVtLkiz