# Author: cr4zjh0bp

# Created: Sun Mar 22 23:25:40 UTC 2020

import sys

 

stdin = sys.stdin

inf = 1 << 60

mod = 1000000007

 

ni      = lambda: int(ns())

nin     = lambda y: [ni() for _ in range(y)]

na      = lambda: list(map(int, stdin.readline().split()))

nan     = lambda y: [na() for _ in range(y)]

nf      = lambda: float(ns())

nfn     = lambda y: [nf() for _ in range(y)]

nfa     = lambda: list(map(float, stdin.readline().split()))

nfan    = lambda y: [nfa() for _ in range(y)]

ns      = lambda: stdin.readline().rstrip()

nsn     = lambda y: [ns() for _ in range(y)]

ncl     = lambda y: [list(ns()) for _ in range(y)]

nas     = lambda: stdin.readline().split()



from collections import Counter



s = ns()

c = Counter(s)

print(("yes" if len(s) == len(c) else "no"))
# Author: cr4zjh0bp

# Created: Sun Mar 22 23:25:40 UTC 2020

import sys

 

stdin = sys.stdin

inf = 1 << 60

mod = 1000000007

 

ni      = lambda: int(ns())

nin     = lambda y: [ni() for _ in range(y)]

na      = lambda: list(map(int, stdin.readline().split()))

nan     = lambda y: [na() for _ in range(y)]

nf      = lambda: float(ns())

nfn     = lambda y: [nf() for _ in range(y)]

nfa     = lambda: list(map(float, stdin.readline().split()))

nfan    = lambda y: [nfa() for _ in range(y)]

ns      = lambda: stdin.readline().rstrip()

nsn     = lambda y: [ns() for _ in range(y)]

ncl     = lambda y: [list(ns()) for _ in range(y)]

nas     = lambda: stdin.readline().split()



s = ns()

print(("yes" if len(s) == len(set(s)) else "no"))
# Author: cr4zjh0bp
# Created: Sun Mar 22 23:25:40 UTC 2020
import sys

stdin = sys.stdin
inf = 1 << 60
mod = 1000000007
ni = lambda: int(ns())
nin = lambda y: [ni() for _ in range(y)]
na = lambda: list(map(int, stdin.readline().split()))
nan = lambda y: [na() for _ in range(y)]
nf = lambda: float(ns())
nfn = lambda y: [nf() for _ in range(y)]
nfa = lambda: list(map(float, stdin.readline().split()))
nfan = lambda y: [nfa() for _ in range(y)]
ns = lambda: stdin.readline().rstrip()
nsn = lambda y: [ns() for _ in range(y)]
ncl = lambda y: [list(ns()) for _ in range(y)]
nas = lambda: stdin.readline().split()
from collections import Counter

s = ns()
c = Counter(s)
print(("yes" if len(s) == len(c) else "no"))

# Author: cr4zjh0bp
# Created: Sun Mar 22 23:25:40 UTC 2020
import sys

stdin = sys.stdin
inf = 1 << 60
mod = 1000000007
ni = lambda: int(ns())
nin = lambda y: [ni() for _ in range(y)]
na = lambda: list(map(int, stdin.readline().split()))
nan = lambda y: [na() for _ in range(y)]
nf = lambda: float(ns())
nfn = lambda y: [nf() for _ in range(y)]
nfa = lambda: list(map(float, stdin.readline().split()))
nfan = lambda y: [nfa() for _ in range(y)]
ns = lambda: stdin.readline().rstrip()
nsn = lambda y: [ns() for _ in range(y)]
ncl = lambda y: [list(ns()) for _ in range(y)]
nas = lambda: stdin.readline().split()
s = ns()
print(("yes" if len(s) == len(set(s)) else "no"))

-from collections import Counter - -c = Counter(s) -print(("yes" if len(s) == len(c) else "no")) +print(("yes" if len(s) == len(set(s)) else "no"))