Flipper

using System;
using System.Linq;
using System.Collections.Generic;
using System.Numerics;

 static class bitove
     {
      public static void Main()
         {

         long  x = long.Parse(Console.ReadLine());
         string s =Convert.ToString(x,2);
         //Console.WriteLine(s);
         ulong[] bits = s.Select(c => ulong.Parse(c.ToString())).ToArray();
         for (int i = 0; i < bits.Length-2; i++)
             {
             if ((bits[i]==bits[i+1])&(bits[i+1]==bits[i+2]))
                 {
                 bits[i] ^= 1;
                 bits[i+1] ^= 1;
                 bits[i+2] ^= 1;
                 i += 2;
                 }
             }
         List<ulong> output = new List<ulong>();
         foreach (var bit in bits)
             {
             output.Add(bit);
             }
         //for (int i = 0; i < output.Count; i++)
         //    {
         //    Console.Write(output[i]);
         //    }
         string[] result = output.Select(c => c.ToString()).ToArray();
         string result2 = string.Join("", result);
         //Console.WriteLine();
         Console.WriteLine(Convert.ToUInt64(result2, 2));
         }
     }