1 #include <iostream>
 2 #include <cstdio>
 3 #include <cmath>
 4 using namespace std;
 5 double node[110],map[110][110],Min,n;
 6 const double INF=999999999;
 7 
 8 double prim()
 9 {
10     int vis[110]= {0};
11     int tm=1,m;
12     double sum=0;
13     vis[tm]=1;
14     node[tm]=0;
15     for (int k=2; k<=n; k++)
16     {
17         Min=INF;
18         for (int i=1; i<=n; i++)
19             if (!vis[i])
20             {
21                 if (node[i]>map[tm][i])
22                     node[i]=map[tm][i];
23                 if (Min>node[i])
24                 {
25                     Min=node[i];
26                     m=i;
27                 }
28             }
29         vis[m]=1;
30         tm=m;
31         sum+=node[m];
32     }
33     //for (int i=1; i<=n; i++)
34     //sum+=node[i];
35     return sum;
36 }
37 
38 int main ()
39 {
40     double a[110],b[110];
41     while (cin>>n)
42     {
43         for (int i=1; i<=n; i++)
44             cin>>a[i]>>b[i];
45         for (int i=1; i<=n; i++)
46         {
47             node[i]=INF;
48             for (int j=1; j<=n; j++)
49                 map[i][j]=INF;
50         }
51         for (int i=1; i<=n; i++)
52         {
53             for (int j=1; j<=n; j++)
54             {
55                 map[i][j]=map[j][i]=sqrt((a[i]-a[j])*(a[i]-a[j])+(b[i]-b[j])*(b[i]-b[j]));
56             }
57         }
58         printf ("%.2lf\n",prim());
59     }
60     return 0;
61 }