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);
$A=str_split($S);
$c=0;
for ($i=0; $i <count($A) ; $i++) {
  // code...
  for ($j=$i+1; $j <count($A) ; $j++) {
    // code...
    if($A[$i]==$A[$j]){
      $c++;
      break 2;
    }
  }
}
if($c==0){
  echo "yes";
}else{
  echo "no";
}
 ?>