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;

class Program
{
    static void Main(string[] args)
    {
        bool[] used = new bool[26];

        string input = Console.ReadLine();

        for(int i = 0; i < input.Length; i++)
        {
            if (used[input[i] - 'a'])
            {
                Console.WriteLine("no");
                break;
            }
            else used[input[i] - 'a'] = true;
            if (i == input.Length - 1)
            {
                Console.WriteLine("yes");
            }
        }
    }
}