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;

public class Solution
{
    public static void Main()
    {
        var s = Console.ReadLine();

        var list = new HashSet<char>();

        foreach (var c in s)
        {
            if (list.Contains(c))
            {
                Console.WriteLine("no");
                return;
            }
            list.Add(c);
        }
        Console.WriteLine("yes");
    }
}