instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
EyvnjbVLF, vqnjblzR
answer:
njb


question:
NwmTIZSnlKGG, qAYIZSnfWRd
answer:
IZSn


question:
kWnjCoVmCSVuW, RILPKCoVmCSVbaOza
answer:

CoVmCSV