3

using System;

namespace FibonacciSum
{
    class Program
    {
        static long Fibonacci(long n)
        {
            if (n <= 1)
            {
                return n;
            }
            else
            {
                return Fibonacci(n - 1) + Fibonacci(n - 2);
            }
        }

        static void Main(string[] args)
        {
            long n = 4000000000;
            long sum = Fibonacci(n / 3) * 2 + Fibonacci(n / 2);
            Console.WriteLine("Sum: " + sum);
        }
    }
}