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 PHP (5.6.30) (judge verdict: Accepted)

<?php
	$s=fgets(STDIN);
	for($i=0;$i<strlen($s);$i++){
		for($j=$i+1;$j<strlen($s);$j++){
			$f+=$s[$i]==$s[$j];
		}
	}
	echo $f?no:yes;