You are given a string S consisting of lowercase English letters. Determine whether all the characters in S are different.
s = input()
for i in s:
    if s.count(i) >= 2:
        print("no")
    else:
        print("yes")
s = input()
for i in s:
    if s.count(i) >= 2:
        print('no')
        exit()
else:
	print('yes')