#include <stdio.h>
#include <iostream>
#include <math.h>

using namespace std;

double GetAnswer(int N,int *xs,int *ys);

int main(void){
  int N;
  double ans;
  int *xs,*ys;
  char buf[20];
  while(true){
    cin >> N;
    if(N==0) break;
    xs = new int[N];
    ys = new int[N];
    for(int i=0;i<N;i++){
      cin >> xs[i];
      cin >> ys[i];
    }
    
    ans = GetAnswer(N,xs,ys);
    delete[] xs;
    delete[] ys;
    sprintf(buf,"%.1f",ans);
    cout << buf<<endl;
    
  }
  return 0;
  
}

double GetAnswer(int N,int *xs,int *ys){
  static const double hpi = asin(1);
  int nowx,nowy;
  int diffx,diffy;
  int left;
  bool *visited = new bool[N];
  double *angle = new double[N];
  double *diff   = new double[N];
  double now_angle = hpi;
  double ans = 0;
  double diff_angle,tmp;
  int trg_flag;
  nowx = nowy = 0;
  left = N;
  for(int i=0;i<N;i++) visited[i] = false;
  for(int left=N ; left>0 ; left--){
    // calculate diff, angle
    for(int i=0;i<N;i++){
      if(visited[i]) continue;
      diffx = xs[i] - nowx;
      diffy = ys[i] - nowy;
      diff[i] = sqrt(diffx*diffx + diffy*diffy);
      if(diffx == 0){
	angle[i] = (diffy>0 ? hpi : -hpi); 
      }else{
	angle[i] = atan2(diffy,diffx);
      }
      
    }
    // find next flag
    diff_angle = -1;  // less than 0;
    for(int i=0;i<N;i++){
      if(visited[i]) continue;
      tmp = angle[i] - now_angle;
      while(tmp<=0)    tmp+= 4*hpi; 
      while(tmp>4*hpi) tmp-= 4*hpi; 
      
      if(diff_angle < tmp || (diff_angle==tmp && diff[i] < diff[trg_flag])){
      	diff_angle = tmp;
	trg_flag   = i;
      }
    }
    ans += diff[trg_flag];
    visited[trg_flag] = true;
    nowx = xs[trg_flag];
    nowy = ys[trg_flag];
    now_angle = angle[trg_flag];
  }
  delete[] visited;
  delete[] angle;
  delete[] diff;
  return ans;
}