#include <cstdio>

 #include <cmath>

 #include <algorithm>

 #include <iostream>

 #include <cstring>

 #include <queue>

 #include <vector>

 #define maxn 115

 using namespace std;

 const int INF = 0x3f3f3f;

 struct Point{

     double x,y;

     bool operator < (const Point & rh) const{

         return y < rh.y  || (y == rh.y && x < rh.x);

     }

 }p[maxn];

 int n;

 double ans;

 double G[maxn][maxn];

 double calculate(int i,int j){

     double xx = p[j].x - p[i].x;

     double yy = p[j].y - p[i].y;

     return sqrt(xx*xx + yy*yy);

 }

 void prim(){

     bool vis[maxn];

     double lowdist[maxn];

     double mindist;

     memset(vis,,sizeof(vis));

     for(int i=;i<=n;i++) lowdist[i]=INF;

     int point;

     int s=;

     vis[s] =true;

     int num=;

     while(true){

         if(num == n) break;

         vis[s]=true;

         mindist = INF;

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

             if(!vis[i] && lowdist[i] > G[s][i]){

                 lowdist[i] = G[s][i];

             }

             if(!vis[i] && mindist  > lowdist[i]){

                 mindist=lowdist[i];

                 point = i;

             }

         }

         s = point;

         ans += mindist;

         num++;

     }

     return;

 }

 int main()

 {

 //    if(freopen("input.txt","r",stdin)== NULL)  {printf("Error\n"); exit(0);}

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

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

             scanf("%lf%lf",&p[i].x,&p[i].y);

         }

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

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

              G[i][j] = G[j][i] = calculate(i,j);

            }

            ans = ;

            //print();

         prim();

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

     }

 }