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

namespace yc53cs
{
    class Program
    {
        static Decimal[] Cache = new Decimal[99];
        static bool[] bWroteCache = new bool[99];
        static void Main(string[] args)
        {
            int N = int.Parse(Console.ReadLine());

            for (int i = 0; i < Cache.Length; i++)
            {
                Cache[i] = 0;
                bWroteCache[i] = false;

            }

            Console.WriteLine(Calc(N));
        }

        static Decimal Calc(int k)
        {
            if (k == 0)
            {
                return 4;
            }
            else if (k == 1)
            {
                return 3;
            }
            else
            {
                if (bWroteCache[k - 2]) return Cache[k - 2];
                Cache[k - 2] = (19 * Calc(k - 1) - 12 * Calc(k - 2)) / 4;
                bWroteCache[k - 2] = true;
                return Cache[k - 2];
            }
        }
    }
}