#include <iostream>

 #include <cstring>

 #include <cstdlib>

 #include <cstdio>

 #include <cmath>

 #include <cctype>

 #include <algorithm>

 #include <numeric>

 #include <limits.h>

 #define typec double

 using namespace std;

 const int inf = 0xffff;

 const int V = ;

 int vis[V];

 typec lowc[V], Map[V][V], point[V][];

 typec prim (typec cost[][V], int n) {

     int i, j, p;

     typec minc, res = ;

     memset(vis, , sizeof(vis));

     vis[] = ;

     for (i = ; i < n; ++ i) lowc[i] = cost[][i];

     for (i = ; i < n; ++ i) {

         minc = inf;

         p = -;

         for (j =  ; j < n; ++ j) {

             if ( == vis[j] && minc > lowc[j]) {

                 minc = lowc[j];

                 p = j;

             }

         }

         if (inf == minc) return -;

         res += minc;

         vis[p] = ;

         for (j =  ; j < n; ++ j) {

             if ( == vis[j] && lowc[j] > cost[p][j]) {

                 lowc[j] = cost[p][j];

             }

         }

     }

     return res;

 }

 double cal_dis (double x1, double y1, double x2, double y2) {

     return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));

 }

 int main () {

     int n;

     while (~scanf("%d", &n)) {

         for (int i =  ; i < n; ++ i) {

             scanf("%lf %lf", &point[i][], &point[i][]);

         }

         for (int i =  ; i < V; ++ i) {

             for (int j = ; j < V; ++ j) {

                 if (i == j) Map[i][j] = ;

                 else Map[i][j] = inf;

             }

         }

         for (int i = ; i < n; ++ i) {

             for (int j = i + ; j < n; ++ j) {

                 Map[i][j] = Map[j][i] =

                     cal_dis(point[i][], point[i][], point[j][], point[j][]);

             }

         }

         //cout << prim(Map, n) << endl;

         printf("%.2lf\n", prim(Map, n));

     }

     return ;

 }