Printing the max length substring with max repetition count

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

namespace ConsoleApplication3
{
    class Program
    {
        static void Main(string[] args)
        {
            string str = Console.ReadLine();
            int[] maxcount = new int[str.Length + 1];
            string[] maxstring = new string[str.Length + 1];
            for (int i = 0; i < str.Length; i++)//Starting point of the substring to be searched.
            {
                for (int length = 1; length <= str.Length - i; length++)//Length of the substring to be searched.
                {
                    int count = 0;
                    string substr1 = str.Substring(i, length);
                    for (int j = 0; j <= str.Length - length; j++)//Starting point in the string from where the search starts.
                    {
                        string substr2 = str.Substring(j, length);
                        if (substr1 == substr2)
                        {
                            count++;
                        }
                    }
                    if (maxcount[length] < count)
                    {
                        maxcount[length] = count;
                        maxstring[length] = substr1;
                    }
                }
            }
            int maxcnt = 0;
            string maxstr="";
            for (int i = 1; i <= str.Length; i++)
            {
                if (maxcnt <= maxcount[i])
                {
                    maxcnt = maxcount[i];
                    maxstr = maxstring[i];
                }
            }
            Console.WriteLine(maxstr + " has the max length: " + maxcnt);
        }
    }
}
abcabcabcabc
abc has the max length: 4
Press any key to continue . . .