#include <stdio.h>

#include <iostream>

#include <string.h>

#include <algorithm>

#include <math.h>

using namespace std;

const int N = ;

struct Point {

    double x,y;

}p[N];

struct Edge{

    int s,e;

    double len;

}edge[N*(N-)/];

int father[N],n;

double dis(Point a,Point b){

    return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));

}

int _find(int x){

    if(x==father[x]) return x;

    return _find(father[x]);

}

int cmp(Edge a,Edge b){

    return a.len<b.len;

}

double kruskal(int m){

    sort(edge+,edge+m+,cmp);

    double cost=;

    for(int i=;i<=m;i++){

        int x = _find(edge[i].s);

        int y = _find(edge[i].e);

        if(x!=y){

            father[x] = y;

            cost +=edge[i].len;

        }

    }

    return cost;

}

int main(){

    while(scanf("%d",&n)!=EOF){

        for(int i=;i<n;i++) father[i] = i;

        for(int i=;i<n;i++){

            scanf("%lf%lf",&p[i].x,&p[i].y);

        }

        int m =; ///边的数量

        for(int i=;i<n;i++){

            for(int j=i+;j<n;j++){ ///这里是i+1开始,从0开始会多出很多边

                edge[m].s =i;

                edge[m].e = j;

                edge[m++].len = dis(p[i],p[j]);

            }

        }

        m--; ///记得

        printf("%.2lf\n",kruskal(m));

    }

}