#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;

struct Point{
	int x, y, index;
	Point(int x, int y, int idx){
		this->x = x;
		this->y = y;
		this->index = idx;
	}
};

void createCombinations(vector  arr, string out, int i, int n, int k, vector  &results){
	if(k == 0){
		results.push_back(out);
		return;
	}
	for(int j = i; j < n; j++){
		createCombinations(arr, out + " " + to_string(arr[j]), j + 1, n, k - 1, results);
	}
}

double calculateDistance(int x1, int y1, int x2, int y2){
	return sqrt(pow(x2 - x1, 2) + pow(y2 - y1, 2));
}

bool compareDistance(pair  p1, pair  p2){
	return calculateDistance(p1.first.x, p1.first.y, p1.second.x, p1.second.y) < calculateDistance(p2.first.x, p2.first.y, p2.second.x, p2.second.y);
}

void solve(vector  houses){
	const int n = houses.size();
	vector > points;
	vector  distances;
	vector  flag(n, false);
	vector  index(n * (n - 1) / 2);
	vector  combinations;

	for(int i = 0; i < index.size(); i++){
		index[i] = i;
	}
	createCombinations(index, "", 0, n * (n - 1) / 2, n / 2, combinations);

	for(int i = 0; i < n; i++){
		for(int j = i + 1; j < n; j++){
			points.push_back({houses[i], houses[j]});
		}
	}
	for(int i = 0; i < n * (n - 1) / 2; i++){
		distances.push_back(calculateDistance(points[i].first.x, points[i].first.y, points[i].second.x, points[i].second.y));
	}

	int pair;
	bool valid;
	double sum = 10e9, temp = 0;
	for(int i = 0; i < combinations.size(); i++){
		fill(flag.begin(), flag.end(), false);
		temp = 0;
		valid = true;
		stringstream ss(combinations[i]);
		while(ss >> pair){
			if(!flag[points[pair].first.index] && !flag[points[pair].second.index]){
				temp += distances[pair];
				flag[points[pair].first.index] = true;
				flag[points[pair].second.index] = true;
			}else{
				valid = false;
				break;
			}
		}
		if(valid){
			sum = min(sum, temp);
		}
		ss.clear();
	}
	cout << fixed << setprecision(2) << sum << " ";
}

int main(){
	int n, x, y, index;
	vector  houses;
	string temp;
	getline(cin, temp);
	stringstream stream(temp);
	while(stream >> n){
		index = 0;
		houses.reserve(2 * n);
		for(int i = 0; i < 2 * n; i++){
			stream >> x >> y;
			Point p(x, y, index++);
			houses.push_back(p);
		}
		solve(houses);
		houses.clear();
	}
	return 0;
}