Multiple of 3 and 5

#include<bits/stdc++.h>
using namespace std;
#define fast()(ios_base::sync_with_stdio(false),cin.tie(NULL));
int main()
{
    int sum=23,i;
    for(i=10;i<=999;i++)
    {
        if(i%3==0 || i%5==0)sum+=i;
    }
    printf("%d\n",sum);
}