Multiple3n5 -TizzyT

using System;

namespace Multiple3n5
{
    internal class Program
    {
        private static void Main(string[] args)
        {
            bool[] Nbrs = new bool[1000];
            int R = 0;
            for (int i = 3; i < 1000; i += 3)
            {
                Nbrs[i] = true;
                R += i;
            }
            for (int i = 5; i < 1000; i += 5) if (!(Nbrs[i])) R += i;
            Console.WriteLine(R);
            Console.ReadKey();
        }
    }
}