05.Bit Flipper

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Numerics;

class BitFlipper
{
    static void Main()
    {
        ulong input = ulong.Parse(Console.ReadLine());
        string newstring = Convert.ToString((long)input, 2).PadLeft(64,'0');
        char[] bits = newstring.ToCharArray();
        for(int i = 0;i<62;i++)
        {
            if(bits[i] == '0' && bits[i+1] == '0' && bits[i+2] == '0')
            {
                bits[i] = '1';
                bits[i+1] = '1';
                bits[i+2] = '1';
                if (i < 62)
                {
                    i += 2;
                }
            }
            else if(bits[i] == '1' && bits[i + 1] == '1' && bits[i + 2] == '1')
            {
                bits[i] = '0';
                bits[i + 1] = '0';
                bits[i + 2] = '0';
                if(i<62)
                {
                    i += 2;
                }
            }
        }
        string result = "";
        foreach (char ch in bits)
        {
            result += ch;
        }
        ulong s = Convert.ToUInt64(result, 2);
        Console.WriteLine(s);
    }
}