If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.

Find the sum of all the multiples of 3 or 5 below 1000.

**Running time:** Unknown

**Assessment:** First code I’d written in 7-8 years. I hadn’t started measuring execution time yet, so I’m not sure how long it took to run, but it’s basically instantaneous.

`#include <iostream>`

using namespace std;

int main()

`{`

int total = 0;

for (int i = 0; i < 1000; i++)

`{`

if( (i % 3 == 0) || (i % 5 == 0) )

total += i;

`}`

cout << total;

return 0;

`}`

Wrong answer…………

Incorrect.