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
fscanf(STDIN, "%s", $string);


$length = strlen($string);

for($i = 0; $i<$length ; $i++){
    $count = substr_count($string, $string[$i]);

  	if($count > 1){
    	echo 'no';
      	return;
    } 
}

echo 'yes';

?>