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 (2.7.6) (judge verdict: Accepted)

s = raw_input()
a = ord('a')
def check(s):
    for i in xrange(26):
        if s.count(chr(a+i)) >1:
            print "no"
            return 0
    print "yes"
    return 0
check(s)