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;

class Program {
    static void Main (string[] args) {
        long input = long.Parse (Console.ReadLine ());
        long all = input * (input + 1) / 2;
        long three = input - (input % 3);
        long threesum = three * (three + 3) / 6;
        long five = input - (input % 5);
        long fivesum = five * (five + 5) / 10;
        long fifteen = input - (input % 15);
        long fifteensum = fifteen * (fifteen + 15) / 30;
        long minus = threesum + fivesum - fifteensum;
        long ans = all - minus;
        Console.WriteLine (ans);
    }
}