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 C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Linq;
using System.Collections.Generic;
using static System.Console;

class Program {
    static void Main(string[] args) {
        var s = ReadLine();
        Boolean b = true;

        for (int i = 0; i < s.Length; i++) {
            if ((s.Length - s.Replace(s[i].ToString(), "").Length) != 1) {
                b = false;
                break;
            }
        }

        var res = (b) ? "yes" : "no";
        WriteLine(res);
    }
}