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

def main():
    l = sys.stdin.readline()
    dic = {}

    for ch in l:
        if ch in dic:
            print("no")
            return 0
        else:
            dic[ch] = 1

    print("yes")
    return 0

if __name__ == '__main__':
    sys.exit(main())