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.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Text.RegularExpressions;
using System.Globalization;

namespace test
{
    class Program
    {
        static void Main(string[] args)
        {
            String str = Console.ReadLine();
            var data = new HashSet<char>();
            for(int i = 0; i < str.Count(); i++)
            {
                data.Add(str[i]);
            }
            if (data.Count() == str.Count())
            {
                Console.WriteLine("yes");
            }
            else
            {
                Console.WriteLine("no");
            }
        }
    }
}