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 static System.Math;

class AtCoder{
  public static void Main(){

    string s = Console.ReadLine();
    char[] c = new char[s.Length];
    
    c = s.ToCharArray();
    Array.Sort(c);
    
    bool b = true;
    for (int i = 1; i < s.Length; i++){
        if(c[i] == c[i-1]){
            b = false;
            break;
        }
    }
    if(b) Console.WriteLine("yes");
    else Console.WriteLine("no");
  }
}