instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
yrIDSuVuQU, UXTSuVuLcch
answer:
SuVu


question:
bmsrkXGb, GcarkXOZF
answer:
rkX


question:
lCHqAMKlHnNzqcYcIUtdnQlzQc, DLtMijJwDQlHnNzqcYcIbM
answer:

lHnNzqcYcI