lab 3 ex 17

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int n, s;
    s = 0;

    for (n = 1; n <= 12; ++n ){

        if (n % 3 == 0 ){
        s = s + n;
        }

    }
    printf("%d\n", s);

    return 0;
}