#include <stdio.h>

#define N 1000000
#define REPS 1000

double x[N], y[N];

double ddot(int n, double *x, double *y)
{
    double s;
    int i;

    s = 0.0;
    for (i = 0; i < N; i++) {
	s = s + x[i] * y[i];
    }
    return s;
}

int main()
{
    double s;
    int i, j;

    for (i = 0; i < N; i++)
	x[i] = y[i] = i + 1;

    for (j = 0; j < REPS; j++)
	s = ddot(N, x, y);

    printf("sum = %f\n", s);
    return 0;
}