(笔试题)被3和5整除的数的和

#include <iostream>

using namespace std;

int SumOfArithmeticSeries(int x,int c,int d){
    return (x+x+(c-1)*d)*c/2;
}

int main()
{
    int sum_3=0,sum_5=0,sum_15=0;
    int n=9;
    int sum=0;
    sum_3=SumOfArithmeticSeries(3,n/3,3);
    sum_5=SumOfArithmeticSeries(5,n/5,5);
    sum_15=SumOfArithmeticSeries(15,n/15,15);
    sum=sum_3+sum_5-sum_15;
    cout<<sum<<endl;
    return 0;
}