instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
XjYkMfARxWBSBjuXyDrFt, EtUxIfiHkMfARxWBSckTLTTnR
answer:
kMfARxWBS


question:
SFQHJlK, dHfQHJoUC
answer:
QHJ


question:
JzJzvoQFLF, iqBOxJzvoQlUhT
answer:

JzvoQ