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

namespace test_2
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] n = Console.ReadLine().Split();
            int s = int.Parse(n[0]);

            int count = 0;

            for(int i = 1; i <= Math.Pow(10,s); i++)
            {
                if(i%3 == 0)
                {
                    count++;
                }
                else if (i.ToString().Contains("3"))
                {
                    count++;
                }
            }

            Console.WriteLine(count);
        }
    }
}