#include <stdio.h>
#include <math.h>
#include <string.h>
#define MAX 110
#define INF 1000000000

struct Point{
	double x,y;
};
double graph[MAX][MAX] ;
double prim(int n)
{
	bool visited[MAX];
	memset(visited,false,sizeof(visited));
	double lowcost[MAX] ;
	int closest[MAX] ;
	for(int i = 0 ; i < n ; ++i)
	{
		lowcost[i] = graph[0][i] ;
		closest[i] = 0 ;
	}
	lowcost[0] = 0.0 ;
	visited[0] = false ;
	for(int i = 0 ; i < n ; ++i)
	{
		int min = INF , index = 0 ;
		for(int j = 0 ; j < n ; ++j)
		{
			if(!visited[j] && lowcost[j]<min)
			{
				index = j ;
				min = lowcost[j] ;
			}
		}
		visited[index] = true ;
		for(int j = 0 ; j < n ; ++j)
		{
			if(!visited[j] && lowcost[j]>graph[index][j])
			{
				lowcost[j] = graph[index][j] ;
				closest[j] = index ;
			}
		}
	}
	double sum = 0.0 ;
	for(int i = 1 ; i < n ; ++i)
	{
		sum += lowcost[i] ;
	}
	return sum ;
}

double distance(const Point &a ,const Point &b)
{
	double x = a.x-b.x , y = a.y-b.y ;
	return sqrt(x*x+y*y);
}

int main()
{
	Point p[MAX];
	int n ;
	while(~scanf("%d",&n))
	{
		for(int i = 0 ; i < n ; ++i)
		{
			scanf("%lf%lf",&p[i].x,&p[i].y) ;
		}
		for(int i = 0 ; i < n ; ++i)
		{
			for(int j = 0 ; j <= i ; ++j)
			{
				graph[i][j] = graph[j][i] = distance(p[i],p[j]) ;
			}
		}
		double sum = prim(n) ;
		printf("%.2lf\n",sum) ;
	}
	return 0 ;
}

#include <cstdio>
#include <cmath>
#include <cstring>
#include <algorithm>
#define MAX 110
#define INF 1000000000

using namespace std ;

struct Point{
	double x,y;
};

struct Edge{
	int x , y ;
	double w ;
}edge[MAX*MAX];

bool cmp(const Edge &a ,const Edge &b)
{
	return a.w<b.w ;
}
int f[MAX] ;
void init()
{
	for(int i = 0 ; i < MAX ; ++i)
	{
		f[i] = i ;
	}
}
int find(int x)
{
	int r = x ;
	while(r != f[r])
	{
		r = f[r] ;
	}
	
	int temp ;
	while(x != f[x])
	{
		temp = f[x] ; 
		f[x] = r ;
		x = temp ;
	}
	return r;
}
double kruskal(int m ,int n)
{
	sort(edge,edge+m,cmp) ;
	double lowcost[MAX] ;
	int index = 0 ;
	init() ;
	for(int i = 0 ; i < m ; ++i)
	{
		int fx = find(edge[i].x) , fy = find(edge[i].y) ;
		if(fx != fy)
		{
			lowcost[index++] = edge[i].w ;
			f[fx] = fy ;
		} 
	}
	double sum = 0 ;
	for(int i = 0 ; i < n-1 ; ++i)
	{
		sum += lowcost[i] ;
	}
	return sum ;
}

double dis(const Point &a ,const Point &b)
{
	double x = a.x-b.x , y = a.y-b.y ;
	return sqrt(x*x+y*y);
}

int main()
{
	Point p[MAX];
	int n ;
	while(~scanf("%d",&n))
	{
		for(int i = 0 ; i < n ; ++i)
		{
			scanf("%lf%lf",&p[i].x,&p[i].y) ;
		}
		int index = 0 ;
		for(int i = 0 ; i < n ; ++i)
		{
			for(int j = 0 ; j <= i ; ++j)
			{
				edge[index].x = i , edge[index].y = j ;
				edge[index].w = dis(p[i],p[j]) ;
				index++ ;
			}
		}
		double sum = kruskal(index , n) ;
		printf("%.2lf\n",sum) ;
	}
	return 0 ;
}