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 PHP7 (7.0.15) (judge verdict: Accepted)

<?php
list($s) = strs();
echo count(array_unique(str_split($s))) === strlen($s) ? 'yes' : 'no';
function strs()
{
    return explode(' ', trim(fgets(STDIN)));
}