#include <iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<climits>
using namespace std;
const int maxn=105;
double mp[maxn][maxn];
double dis[maxn],x[maxn],y[maxn];
int vis[maxn];
int i,j,n,l,k;
double minn,sum;

int main()
{
    while(~scanf("%d",&n))
    {
        memset(vis,0,sizeof(vis));
        for(i=1;i<=n;i++) scanf("%lf%lf",&x[i],&y[i]);
        for(i=1;i<=n;i++)
            for(j=i+1;j<=n;j++)
            {
                double d=sqrt(pow(x[i]-x[j],2)+pow(y[i]-y[j],2));
                mp[i][j]=d;
                mp[j][i]=d;
            }
     sum=0;
     vis[1]=1;
     for(i=1;i<=n;i++) dis[i]=mp[1][i];
    for(i=1;i<n;i++)
    {
        minn=INT_MAX*1.0;
        for(j=1;j<=n;j++)
            if(!vis[j] && minn>dis[j])
            {
                k=j;
                minn=dis[j];
            }
        vis[k]=1;
        sum+=minn;
        for(j=1;j<=n;j++)
         if (!vis[j] && dis[j]>mp[k][j])
            dis[j]=mp[k][j];
    }
        printf("%.2lf\n",sum);
    }
    return 0;
}