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 Ruby (2.7.1) (judge verdict: Accepted)

N = gets.chomp.to_i

ans = (N * (N + 1)) / 2
# puts ans

numOf3s = N / 3
numOf5s = N / 5
numOf15s = N / 15

threes = 0
fives = 0
fifteens = 0

for i in 1..numOf3s do
    threes += i * 3
end

for i in 1..numOf5s do
    fives += i * 5
end

for i in 1..numOf15s do
    fifteens += i * 15
end

# puts threes, fives, fifteens

ans = ans - threes - fives + fifteens

puts ans