1 #include <cmath>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <iostream>
 5 using namespace std;
 6 const int INF = 0x3f3f3f3f;
 7 double map[110][110], dis[110]; bool vis[110];
 8 int n;
 9 struct point
10 {
11     double x, y;    
12 } num[110];
13 double Prim()
14 {
15     memset(vis, true, sizeof(vis));
16     for(int i = 1; i <= n; i++)
17         dis[i] = map[1][i];
18     vis[1] = false;  double sum = 0.0;
19     for(int i = 1; i < n; i++)
20     {
21         int temp; double min = INF;
22         for(int j = 1; j <= n; j++)
23         {
24             if(vis[j] && dis[j] < min)
25             {
26                 temp = j;
27                 min = dis[j];
28             }
29         }
30         vis[temp] = false;
31         sum += min;
32         for(int j = 1; j <= n; j++)
33         {
34             if(vis[j] && dis[j] > map[temp][j])
35                 dis[j] = map[temp][j]; 
36         }
37     }
38     return sum;
39    // printf("%.2lf\n", sum); 
40 }
41 int main()
42 {
43     while(~scanf("%d", &n))
44     {
45         for(int i = 1; i <= n; i++)
46             scanf("%lf %lf", &num[i].x, &num[i].y);
47         for(int i = 1; i <= n; i++)
48         {
49             map[i][i] = 0.0;
50             for(int j = 1; j < i; j++)   
51                 map[j][i] = map[i][j] = sqrt((num[i].x - num[j].x)*(num[i].x - num[j].x) + (num[i].y-num[j].y)*(num[i].y-num[j].y));   
52         }
53         printf("%.2lf\n",Prim());
54     }
55     return 0;
56 }