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

#include <sys/times.h>		/* needed for timer() */
#include <time.h>		/* needed for timer() */

/* function to return elapsed time since last reboot, in seconds */
double timer(void) {
  struct tms t;
  clock_t ticks = times(&t);
  return ((double) ticks)/ CLK_TCK;
}

/* main program */
int main(int argc, char* argv[]) {

    int N = 0;
    double * a;
    int i;
    double sum = 0.0;
    double product = 1.0;
    double start_time;
    double end_time;

    if ((argc < 2) || ((N = atoi(argv[1])) <= 0)) {
        fprintf(stderr, "Usage:  %s number_of_elements\n", argv[0]);
        return 1;
    }

    start_time = timer();

    a = malloc(sizeof(double) * N);  
    if (a == NULL) {
        fprintf(stderr, "Unable to allocate memory for N = %d\n", N);
        return 1;
    }
    for (i=0; i < N; ++i) 
        a[i] = ((double) (i+1))/N;
    for (i=0; i < N; ++i) 
        sum = sum + a[i];
    for (i=0; i < N; ++i) 
        product = product * a[i] + 1;

    end_time = timer();

    fprintf(stdout, "N = %d, sum = %g, product = %g, time = %g\n", 
            N, sum, product, end_time - start_time);
    return 0;
}