using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        string s = "au";

          int result = LengthOfLongestSubstring(s);

​

        Console.WriteLine(s[1]);

        Console.WriteLine(result);

    }

     public static int LengthOfLongestSubstring(string s) {

        char[] sa = s.ToCharArray();

        List<char> subs = new List<char>();

          int strl = 0; int maxstr =0;

        if(sa.Count() > 0){

        for(int i =0; i<sa.Length; i++){

            subs = new List<char>();

              subs.Add(sa[i]);     

             strl =subs.Count();

           for(int j =1; j<sa.Length; j++)

           {

               if(!subs.Contains(sa[j]))

               {

                   subs.Add(sa[j]);

                  strl = subs.Count();

               }   

             else

             {   

                 Console.WriteLine("max str = " +  maxstr);

                 Console.WriteLine("str l " + strl);

              maxstr = maxstr > strl ? maxstr : strl;

              subs = new List<char>();

              subs.Add(sa[j]);

              strl =subs.Count();

            } 

           }

           } 

        return maxstr;

    }

    else return 0;

    }

}