instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
LJJvLTK, jpFJvLqh
answer:
JvL


question:
cxYVucnmEQopeWHrPJ, jNnOaYVucnmEQoSE
answer:
YVucnmEQo


question:
cIrLDaH, wJrLDxu
answer:

rLD