instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
CxosNa, ikosdx
answer:
os


question:
aWshKwEuYBBdSwIAyXw, wfVuYBBdSwIAseTxR
answer:
uYBBdSwIA


question:
lPhVhAQZWJDrvzcEaGEwKgZAuJI, qIJDrvzcEaGDRCRrB
answer:

JDrvzcEaG