void average(int* num_of_items, double* average)
{
	if (average != NULL) {
		double temp, av;
		double sum = 0.0;
		int i;
		for (i = 0; i < *num_of_items; i++)
		{
			scanf("%lf", &temp);
			if (temp < 0)
				break;
			sum+=temp;
		}
		av = sum/(*num_of_items);
		*average = av;
	}
	else
		return;

}