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;
public class Hello{
    public static void Main(){
        string input = Console.ReadLine();
        bool flag = true;
        
        for(int x = 0;x < input.Length - 1;x++){
            for(int y = x + 1;y < input.Length;y++){
                if(input.Substring(x,1) == input.Substring(y,1)){
                    flag = false;
                    break;
                }
            }
        }
        
        if(flag == true){
            Console.WriteLine("yes");
        }else{
            Console.WriteLine("no");
        }
    }
}