instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
jJjsASFfCqVV, AkjsASFfBFwPy
answer:
jsASFf


question:
HXYkGv, GCYksu
answer:
Yk


question:
MjjKLoIsYzIdoJULAO, BMtFlojKLoIsYzzYxd
answer:

jKLoIsYz