/*
 * This program checks the length of a tour.  Give the points data file
 * name on the command line.
 */
#include <stdio.h>
#include <math.h>

typedef struct _point {
	float	x, y, z;
} point;

float distance (point v[], int i, int j) {
	float	dx, dy, dz;

	dx = v[i].x - v[j].x;
	dy = v[i].y - v[j].y;
	dz = v[i].z - v[j].z;
	return sqrt (dx*dx + dy*dy + dz*dz);
}

float tour_length (int tour[], point v[], int n) {
	int	i, from, to;
	float	sum;

	/* sum up distances between cities on the tour */
	
	sum = 0;

	/* start at city 0 */

	from = 0;
	for (i=1; i<n; i++) {

		/* find distance to next city in tour */

		to = tour[i];

		/* add that to the length of the tour */

		sum += distance (v, from, to);

		/* the next source is the current target */

		from = to;
	}

	/* add in the distance back to the first city */

	sum += distance (v, from, 0);
	return sum;
}

int main (int argc, char *argv[]) {
	char	present[1000];
	int	i, j, n, tour[1000];
	float	length, min;
	point	cities[1000];
	FILE	*f;

	if (argc != 2) {
		fprintf (stderr, "Usage: %s <filename>\n", argv[0]);
		exit (1);
	}
	f = fopen (argv[1], "r");
	if (!f) {
		perror (argv[1]);
		exit (1);
	}
	fscanf (f, "%d\n", &n);
	for (i=0; i<n; i++) {
		fscanf (f, "%f %f %f\n", &cities[i].x, &cities[i].y, &cities[i].z);
	}
	fclose (f);
	bzero (present, n);
	for (i=0; i<n; i++) {
		scanf ("%i", &tour[i]);
		if (feof (stdin)) {
			fprintf (stderr, "unexpected end of file!\n");
			exit (1);
		}
		if (tour[i] >= 0 && tour[i] < n) 
			present[i] = 1;
		else {
			fprintf (stderr, "index %d out of bounds!\n", tour[i]);
			exit (1);
		}
	}
	for (i=0; i<n; i++) if (!present[i]) {
		fprintf (stderr, "not all points in tour, missing %d!\n", i);
		exit (1);
	}
	length = tour_length (tour, cities, n);
	printf ("length of tour is %f\n", length);
	exit (0);
}