Problem:
Score : 200 points

Problem Statement

Let us define the FizzBuzz sequence a_1,a_2,... as follows:

If both 3 and 5 divides i, a_i=\mbox{FizzBuzz}.

If the above does not hold but 3 divides i, a_i=\mbox{Fizz}.

If none of the above holds but 5 divides i, a_i=\mbox{Buzz}.

If none of the above holds, a_i=i.

Find the sum of all numbers among the first N terms of the FizzBuzz sequence.

Constraints

1 \leq N \leq 10^6

Input

Input is given from Standard Input in the following format:

N

Output

Print the sum of all numbers among the first N terms of the FizzBuzz sequence.

Sample Input 1

15

Sample Output 1

60

The first 15 terms of the FizzBuzz sequence are:

1,2,\mbox{Fizz},4,\mbox{Buzz},\mbox{Fizz},7,8,\mbox{Fizz},\mbox{Buzz},11,\mbox{Fizz},13,14,\mbox{FizzBuzz}

Among them, numbers are 1,2,4,7,8,11,13,14, and the sum of them is 60.

Sample Input 2

1000000

Sample Output 2

266666333332

Watch out for overflow.

Solution in C# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication6
{
    class Program
    {
        static void Main(string[] args)
        {
            var rl = RL();
            //var sprlst = spr(rl);
            //var intlist = sprlst.Select(x => c2i(x)).ToList();
            var k = c2i(rl);
            //var ls1 = Enumerable.Range(0, 10).Select(x => (long)x);
            var fbsum = (k * (k + 1)) / 2;
            var num3 = (k / 3) * 3; 
            var num5 = (k / 5) * 5;
            var num15 = (k / 15) * 15;
            var ans = fbsum - getsum(num3,3)-getsum(num5,5) +getsum(num15,15);

            bool ret = false;



            Console.WriteLine(ans);
            //Console.ReadLine();
            




        
        }
        static Int64 getsum(Int64 last, int ct) { return (ct + last) * (last / ct) / 2; }
        static string RL() { return Console.ReadLine().Trim(); }
        static IEnumerable<string> spr(string s) { return s.Split(' '); }
        static Int64 c2i(string c) { return Int64.Parse(c); }
        //static double c2d(string c) { return double.Parse(c); }
        static string bool2ret(bool b) { return b ? "Yes" : "No"; }
    }
}