#include <stdio.h>
#include <math.h>

typedef struct Point2D {
	int x, y;
} Point2D;

static double solve(Point2D flags[], int number_of_flags);
static double distance(Point2D *pt1, Point2D *pt2);
static int    approx_equal(double num1, double num2, double epsilon);

int main()
{
#ifdef TARGET_RT_MAC_CFM
	FILE *stream = fopen("input", "r");
#else
	FILE *stream = stdin;
#endif
	int     number_of_flags, index;
	Point2D flags[400];
	for (;;) {
		fscanf(stream, "%d", &number_of_flags);
		if (number_of_flags <= 0)
			break;
		for (index = 0; index < number_of_flags; index++)
			fscanf(stream, "%d%d", &flags[index].x, &flags[index].y);
		printf("%.1f\n", solve(flags, number_of_flags));
	}
	return 0;
}

static double solve(Point2D flags[], int number_of_flags)
{
	int     number_of_remaining_flags = number_of_flags;
	Point2D last_point = {0, 0}, direction = {0, 1};
	double  direction_rad = atan2(1, 0), epsilon = atan2(1, 500) / 10.0, two_pi = 3.14159265358979323846 * 2;
	double  result = 0;
	while (number_of_remaining_flags > 0) {
		int    index, best_index = 0, is_first = 1;
		double rad, best_rad;
		for (index = 0; index < number_of_flags; index++) {
			if (flags[index].x < 0)
				continue;
			rad = direction_rad - atan2(flags[index].y - last_point.y, flags[index].x - last_point.x);
			if (rad < 0)
				rad += two_pi;
			if (is_first || rad < best_rad)
				best_rad = rad, best_index = index;
			else if (approx_equal(rad, best_rad, epsilon) && 
					 distance(&last_point, &flags[index]) < distance(&last_point, &flags[best_index]))
				best_rad = rad, best_index = index;
			is_first = 0;
		}
		result += distance(&last_point, &flags[best_index]);
		direction.x = flags[best_index].x - last_point.x, direction.y = flags[best_index].y - last_point.y;
		direction_rad = atan2(direction.y, direction.x);
		last_point = flags[best_index];
		flags[best_index].x = -1;
		number_of_remaining_flags--;
	}
	return result;
}

static double distance(Point2D *pt1, Point2D *pt2)
{
	double dx = pt1->x - pt2->x, dy = pt1->y - pt2->y;
	return sqrt(dx * dx + dy * dy);
}

static int approx_equal(double num1, double num2, double epsilon)
{
	return (fabs(num1 - num2) <= epsilon);
}