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:
IKrQfT, crrQRg
answer:
rQ


question:
GaJozvDHULRlhNJIcKZSpuV, FJFqULRlhNJIcgE
answer:

ULRlhNJIc