#include <iostream>
#include <fstream>
#include <cmath>
#include <vector>
#include <string>
#define INF 99999999999999
using namespace std;

double min = INF;

struct Point
{
	int x;
	int y;
};


double GetWeight(Point a, Point b)
{
	return sqrt(pow((a.x - b.x), 2) + pow((a.y - b.y), 2));
}

bool NotColored(vector <int>& Marked, int& Vertex)
{
	for (int i = 0; i < Marked.size(); ++i)
	{
		if (Marked[i] == Vertex)
			return false;
		else
			return true;
	}
}

void MST(vector<int>& Marked, vector<double>& Distance, vector<vector<double>>& Graph, int& V)
{
	int index = 0;
	for (int i = 0; i < Marked.size(); ++i)
	{
		for (int j = 0; j < V; ++j)
		{
			if (NotColored(Marked, j) && Graph[Marked[i]][j] < min)
			{
				min = Graph[Marked[i]][j];
				index = j;
			}
		}
	}
	Distance[index] = min;
	Marked.push_back(index);
	min = INF;

	if (Marked.size() == V)
	{
		int result = 0;
		for (int i = 0; i < V; ++i)
		{
			if (!NotColored(Marked, i))
			result += Distance[i];
		}
		cout.precision(10);
		cout << result;
		exit(0);
	}
	MST(Marked, Distance, Graph, V);


}

int main()
{
	int V, index = 0;
	cin >> V;
	vector <Point> Points(V);
	vector <int> Marked(1);
	vector <double> Distance(V, INF);
	for (int i = 0; i < V; ++i)
		cin >> Points[i].x >> Points[i].y;
	vector<vector<double>> Graph(V, vector <double>(V));

	for (int i = 0; i < V; ++i)
		for (int j = 0; j < V; ++j)
			Graph[i][j] = GetWeight(Points[i], Points[j]);

	Marked[0] = 0;

	for (int i = 1; i < V; ++i)
	{
		if (Graph[0][i] < min)
		{
			min = Graph[0][i];
			index = i;
		}
	}
	Marked.push_back(index);
	Distance[index] = min;
	min = INF;

	MST(Marked, Distance, Graph, V);
	return 0;
}