#include<cmath>
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<algorithm>
using namespace std;
#define x first
#define y second
typedef pair<int,int>pii;
const int N=5050;
const int INF=1e9;
pii p[N];
double dist[N];
bool vis[N];
int n;
double calc(int x1,int y1,int x2,int y2)
{
return sqrt((double)(x1-x2)*(x1-x2)+(double)(y1-y2)*(y1-y2));
}
int main()
{
cin>>n;
for(int i=1; i<=n; i++)
cin>>p[i].x>>p[i].y;
for(int i=2; i<=n; i++)
dist[i]=INF;
double ans=0;
for(int i=1; i<=n; i++)
{
double miv=INF;
int mipoj;
for(int j=1; j<=n; j++)
if(!vis[j]&&dist[j]<miv)
{
mipoj=j;
miv=dist[j];
}
ans+=miv;
vis[mipoj]=1;
for(int j=1; j<=n; j++)
{
double t=calc(p[mipoj].x,p[mipoj].y,p[j].x,p[j].y);
if(t<dist[j])
dist[j]=t;
}
}
printf("%.2lf\n",ans);
return 0;
}