Problem:
Score : 200 points

Problem Statement

You are given a string S consisting of lowercase English letters. Determine whether all the characters in S are different.

Constraints

2 ≤ |S| ≤ 26, where |S| denotes the length of S.

S consists of lowercase English letters.

Input

Input is given from Standard Input in the following format:

S

Output

If all the characters in S are different, print yes (case-sensitive); otherwise, print no.

Sample Input 1

uncopyrightable

Sample Output 1

yes

Sample Input 2

different

Sample Output 2

no

Sample Input 3

no

Sample Output 3

yes

Solution in Python (3.4.3) (judge verdict: Accepted)

import sys
import math
# import decimal
# import queue
# import bisect
# import heapq # priolity-queue
# import time
# import itertools
# import collections # queue
# from operator import itemgetter
# from fractions import Fraction

mod = int(1e9+7)
INF = 1<<29
lINF = 1<<35

def main():
    s = list(input())
    s.sort()
    for i in range(len(s)-1):
        if s[i]==s[i+1]:
            print("no")
            return
    print("yes")
    return

if __name__=='__main__':
    main()