1

using System;

namespace FibonacciSum
{
    class Program
    {
        static void Main(string[] args)
        {
            long sum = 0;
            long a = 1;
            long b = 2;
            while (b < 4000000000)
            {
                if (b % 2 == 0)
                {
                    sum += b;
                }
                long c = a + b;
                a = b;
                b = c;
            }
            Console.WriteLine("Sum: " + sum);
        }
    }
}