using System;

using System.Linq;

public class Program

{

    //If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.

    //Find the sum of all the multiples of 3 or 5 below 1000.

    public static void Main()

    {

        var result = Enumerable.Range(1, 999).Where(x => x % 3 == 0 || x % 5 == 0).Sum();

        Console.WriteLine(result);

    }

}