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 JavaScript (node.js v5.12) (judge verdict: Accepted)

'use strict'

function main(s) {
  const str = s.split('\n')[0].split('');

  const before_len = str.length;
  const after_len = [...new Set(str)].length;

  const ans = (before_len === after_len) ? 'yes' : 'no';
  console.log(ans);
}

main(require("fs").readFileSync("/dev/stdin", "utf8"));