import java.io.BufferedReader;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.StringTokenizer;
import java.lang.Math;
import java.util.ArrayList;
import java.util.PriorityQueue;


public class primMain implements Runnable {
	StringTokenizer st;
	BufferedReader in;
	PrintWriter out;
	double ans;
	static int AAA=2000000000;
	//classes
	public static class Vertex implements Comparable<Vertex> {
		//double d;
		boolean visited;
		Vertex parent;
		long key;
		ArrayList<Edge> adj;

		public int compareTo(Vertex other) {
			Vertex ver = (Vertex) other;
			return (int) (key - ver.key);
		}
		public Vertex() {
			//d=0;
			adj = new ArrayList<Edge>();
			key=AAA;
			visited=false;
		}
	}

	public static class Edge {
		Vertex v1, v2;
		long weight;
	}
	/////////////
	//variables//
	/////////////
	int n;
	long x[];
	long y[];
	Vertex vertexes[];
	PriorityQueue<Vertex> que = new PriorityQueue<Vertex>();

	public static void main(String[] args) {
		new Thread(new primMain()).run();
	}

	public void run() {
		try {
			in = new BufferedReader(new FileReader("spantree.in"));
			out = new PrintWriter(new FileWriter("spantree.out"));
			solve();
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			out.flush();
			out.close();
		}
	}

	String nextToken() throws IOException {
		while (st == null || !st.hasMoreTokens()) {
			st = new StringTokenizer(in.readLine());
		}
		return st.nextToken();
	}

	int nextInt() throws NumberFormatException, IOException {
		return Integer.parseInt(nextToken());
	}

	long nextLong() throws NumberFormatException, IOException {
		return Long.parseLong(nextToken());
	}

	double nextDouble() throws NumberFormatException, IOException {
		return Double.parseDouble(nextToken());
	}
	void Prim (){

		vertexes[0].key=0;

		que.add(vertexes[0]);


		while (!que.isEmpty()) {
			Vertex u;

			u=new Vertex();
			u=que.remove();
			u.visited=true;
			int s=u.adj.size();
			Vertex v;
			v=new Vertex();
			Edge e;
			e=new Edge();
			Vertex vv;
			vv=new Vertex();
			for (int i=0; i<s;i++ ){
				e=u.adj.get(i);
				v=e.v2;
				if (/*(que.contains(v)) &&*/ (e.weight < v.key)&&(v.visited==false)) {
					v.parent=u;
					v.key=e.weight;
					vv=v;
				}
			}
			que.add(v);



		}
	}
	void solve() throws NumberFormatException, IOException {
		n = nextInt();
		x = new long[n];
		y = new long[n];
		vertexes = new Vertex[n];
		for (int i = 0; i < n; i++) {
			x[i] = nextLong();
			y[i] = nextLong();
			vertexes[i]=new Vertex();

		}
		for (int i = 0; i < n; i++) {
			for (int j = 0; j < n; j++) {
				long w =((x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j]));
				Edge e;
				e = new Edge();
				e.v1=vertexes[i];
				e.v2=vertexes[j];
				e.weight=w;
				vertexes[i].adj.add(e);
			}
		}
		Prim();
		for (int i=0;i<n; i++) {
			ans+=Math.sqrt(vertexes[i].key);
		}
		out.println(ans);

	}
}