# coding: utf-8

import sys



S = eval(input())

for s in S:

    if S.count(s)!=1:

        print("no")

        sys.exit()

print("yes")

# coding: utf-8

S = eval(input())

print(("yes" if len(S)==len(set(S)) else "no"))
# coding: utf-8
import sys

S = eval(input())
for s in S:
    if S.count(s) != 1:
        print("no")
        sys.exit()
print("yes")

# coding: utf-8
S = eval(input())
print(("yes" if len(S) == len(set(S)) else "no"))

-import sys - -for s in S: -    if S.count(s) != 1: -        print("no") -        sys.exit() -print("yes") +print(("yes" if len(S) == len(set(S)) else "no"))