using System;

​

public class Program

{

    public static int F(int n)

    {

        if (n == 1)

        {

            return 1;

        }

        else if (n == 2)

        {

            return 2;

        }

        else

        {

            return 5 * F(n) - 4 * F(n - 1) + 3;

        }

    }

​

    public static void Main()

    {

        Console.WriteLine("Enter n:");

        int n = int.Parse(Console.ReadLine());

        float res = F(n);

        Console.WriteLine(res);

    }

}