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 = 10; // Calculate the 10th term in the Fibonacci sequence
            long y = 4000000000; // Sum up to 4,000,000,000
            long fibonacci = Fibonacci(n);
            Console.WriteLine("The " + n + "th term in the Fibonacci sequence is " + fibonacci);

            long sum = Fibonacci(y / 3) * 2 + Fibonacci(y / 2);
            Console.WriteLine("Sum of all even numbers in the