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;
using Console = System.Console;

namespace Atcoder
{
    class Program
    {

        static void Main(string[] args)
        {
            var S = Read();
            string str = string.Empty;
            foreach (var s in S)
            {
                if (str.Contains(s))
                {
                    Console.WriteLine("no");
                    return;
                }
                str += s.ToString();
            }
            Console.WriteLine("yes");
        }
        public static readonly Func<string> Read = () => Console.ReadLine();
        public static readonly Func<string[]> ReadStringArray = () => Console.ReadLine().Split();
        public static readonly Func<int[]> ReadIntArray = () => Console.ReadLine().Split().Select(int.Parse).ToArray();
        public static readonly Func<long[]> ReadLongArray = () => Console.ReadLine().Split().Select(long.Parse).ToArray();
    }
}