#include <stdio.h>
#include <iostream>
#include <string.h>
#include <algorithm>
#include <math.h>
using namespace std;

const int N = 105;
struct Point {
    double x,y;
}p[N];
struct Edge{
    int s,e;
    double len;
}edge[N*(N-1)/2];
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+1,edge+m+1,cmp);
    double cost=0;
    for(int i=1;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=0;i<n;i++) father[i] = i;
        for(int i=0;i<n;i++){
            scanf("%lf%lf",&p[i].x,&p[i].y);
        }
        int m =1; ///边的数量
        for(int i=0;i<n;i++){
            for(int j=i+1;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));
    }
}