instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
zRwQdelc, UdAUwQdejhe
answer:
wQde


question:
MriFNpGM, yaiFNduk
answer:
iFN


question:
SOvpbeexqAvyPUSzJ, PWPIiEexqAvyPyyCJ
answer:

exqAvyP