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 (7.4.4) (judge verdict: Accepted)

<?php
  list($s) = explode(" ", trim(fgets(STDIN)));

  $v=[];
  for($i=0;$i<strlen($s);$i++){
    if(isset($v[$s[$i]])) {
      echo "no".PHP_EOL;
      exit;
    }
    $v[$s[$i]]=true;
  }
  echo "yes".PHP_EOL;