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.Text;
using System.Text.RegularExpressions;
using System.Diagnostics;
using System.Linq;
using System.Collections.Generic;

namespace competitive
{
    class Program
    {
        static void Main(string[] args)
        {
            var s = Console.ReadLine();
            var dict = new Dictionary<char, int>();
            foreach (var c in s)
            {
                if (!dict.ContainsKey(c))
                {
                    dict.Add(c, 1);
                }
                else
                {
                    dict[c]++;
                }
            }
            foreach (var item in dict)
            {
                if (item.Value > 1)
                {
                    System.Console.WriteLine("no");
                    return;
                }
            }
            Console.WriteLine("yes");
        }
    }
}