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;
using static System.Math;
 
public class Hello{
    public static void Main(){
/*        string[] input = ReadLine().Split(' ');
        long a = long.Parse(input[0]);
        long b = long.Parse(input[1]);
        long c = long.Parse(input[2]);
        long d = long.Parse(input[3]);*/
//        string temp = ReadLine();
//        int a = int.Parse(ReadLine());
//        int b = int.Parse(ReadLine());
//        int c = int.Parse(ReadLine());
//        int d = int.Parse(ReadLine());
        string a = ReadLine();
//        string b = ReadLine();
//        string c = ReadLine();
//        string ko = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        int check = 0;
        while(a.Length>0){
            string b = a.Substring(0,1);
            int m = a.Length;
            a = a.Replace(b,"");
            int n = a.Length;
            if(m-n>1){
                check++;
            }
        }
        if(check==0){
            WriteLine("yes");
        }else{
            WriteLine("no");
        }
    }
}