instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
njzfcapS, JDzfcYQh
answer:
zfc


question:
VGRjWGHRcBdFmkVg, eSwqALQXWGHRcBdFsDXCM
answer:
WGHRcBdF


question:
YLnyCA, fsnyRZ
answer:

ny


