instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
QjDQjzAIsnYgNmmetl, vyqDQjzAIsnNajYEheP
answer:
DQjzAIsn


question:
yKtQOhYvrJVH, HQsTQOhYvPP
answer:
QOhYv


question:
OeokBJweaSvCddUQu, rmOmkBJweaSukXg
answer:

kBJweaS