Write a Python program to accept two strings as input and check if they are identical copy of each other or if the second string is a substring of the first string.
ss='Hello w'
ms='Hello world'
if(ss==ms):
print( 'Both the strings are same')
elif(ms.find(ss)!=-1):
print ('{0} is a substring of {1}'.format(ss,ms))
else:
print ('None')