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;

namespace AthleteProgramming2
{
    class Program
    {
        static void Main()
        {
            bool isOk = true;
            int[] all = new int[26];
            for(int i = 0; i < all.Length; i++)
            {
                all[i] = 1;
            }

            char[] s = Console.ReadLine().ToArray();

            for(int i = 0; i < s.Length; i++)
            {
                int tmp = s[i] - 'a';
                all[tmp]--;
            }

            for(int i = 0; i < s.Length; i++)
            {
                if (all[i] <= -1)
                {
                    isOk = false;
                }
            }

            if (isOk == true)
            {
                Console.WriteLine("yes");
            }else
            {
                Console.WriteLine("no");
            }

        }
    }
}