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;

namespace ABC063B
{
    class Program
    {
        static void Main(string[] args)
        {
            string str = Console.ReadLine();
            bool[] chk = new bool[26];

            for (int i = 0; i < str.Length; i++)
            {
                if (chk[str[i] - 'a'])
                {
                    Console.WriteLine("no");
                    return;
                }
                chk[str[i] - 'a'] = true;
            }

            Console.WriteLine("yes");
        }
    }
}