import java.util.*;

class Vertex{
    int x;
    int y;
    int depth;
    Vertex parent;

    public  Vertex (int x, int y) {
        this.x = x;
        this.y = y;
        depth = 0;
        parent = this;
    }
}


//class Length implements Comparable<Length> {
class Length{
    Vertex u;
    Vertex v;
    double len;

    Length(Vertex u, Vertex v, double len) {
        this.len = len;
        this.u = u;
        this.v = v;
    }

    public static Vertex Find(Vertex x) {
        if (x.parent == x)
            return x;
        return Find(x.parent);
    }
    public static void Union(Vertex x, Vertex y) {
        Vertex rootX = Length.Find(x);
        Vertex rootY = Length.Find(y);
        if (rootX.depth < rootY.depth)
            rootX.parent = rootY;
        else {
            rootY.parent = rootX;
            if (rootX.depth == rootY.depth && rootX != rootY)
                rootX.depth++;
        }
    }

}

public class Kruskal {

    /*public static Vertex ExtractMin( PriorityQueue<Length> q) {

        Vertex ptr = q.heap[0];
        if (ptr.x == 0)
            System.out.println("panic");
        q.count--;
        if(q.count > 0) {
            q.heap[0] = q.heap[q.count];
            q.heap[0].index = 0;
            //Heapify(0,q.count,q.heap);
        }
        return ptr;
    }
*/

    public double SpanningTree(PriorityQueue<Length> q) {
        double E = 0;
        for (Length i : q) {
            if (Length.Find(i.u) != Length.Find(i.v)) {
                E = E + i.len;
                Length.Union(i.u, i.v);
            }
        }
        return E;
    }

    public double MST_Kruskal(PriorityQueue<Length> q) {
        //ExtractMin(q);
        return SpanningTree(q);
    }
    public static int N;

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int x, y;
        N = in.nextInt();

        Vertex[] g = new Vertex[N];
        PriorityQueue<Length> q = new PriorityQueue<>(1000);

        for ( int i = 0; i < N; i++) {
             x = in.nextInt();
            y = in.nextInt();
            g[i] = new Vertex(x,y);
        }

        for ( int i = 0; i < N; i++) {
            for (int j = i + 1; j < N; j++) {
                double length = Math.sqrt((g[i].x - g[j].x)*(g[i].x - g[j].x) + (g[i].y - g[j].y)*(g[i].y - g[j].y));
                q.add(new Length(g[i], g[j], length));
                //g[i].lists.add(j);
            }
        }

        Kruskal k = new Kruskal();
        double a = k.MST_Kruskal(q);
        System.out.printf("%.2f",a);

    }
}