instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
TvNVpHLPYjBCeUpyxlzFZ, tgKdPKVYjBCeUpyPK
answer:
YjBCeUpy


question:
nYoRQU, gQoRZQ
answer:
oR


question:
tvffJYmxqmfah, MFvZuYYmxqmfBZh
answer:

Ymxqmf