/**
 * Sample solution for Underground Cables
 *   Steven J Zeil, 10/25/2010
 */
#include <algorithm>
#include <cmath>
#include <fstream>
#include <iostream>
#include <iomanip>

using namespace std;


int x[1000];
int y[1000];
bool connected[1000];
double distanceFromConnectedNodes[1000];

double dist (int i, int j)
{
  double dx = x[i] - x[j];
  double dy = y[i] - y[j];
  return sqrt(dx*dx + dy *dy);
}




/**
 * Process a single dataset for the problem.
 * Return true if successful. Return false if we encounter the
 * end of input marker or an unreocverable I/O error,
 */
bool processDataSet (istream& in)
{
  int N;
  in >> N;
  if (N == 0)
    return false;
  
  for (int i = 0; i < N; ++i)
    {
      in >> x[i] >> y[i];
      connected[i] = false;
      distanceFromConnectedNodes[i] = dist(i,0);;
    }
  connected[0] = true;
  double sum = 0.0;
  int numConnected = 1;
  int lastConnection = 0;
  
  while (numConnected < N)
    {
      // Update distances based on last connection
      int closestNode = -1;
      double closestDist = 0.0;
      for (int i = 0; i < N; ++i)
	{
	  if (!connected[i])
	    {
	      double d = dist(lastConnection, i);
	      distanceFromConnectedNodes[i] = min(distanceFromConnectedNodes[i], d);
	      if (closestNode < 0 || distanceFromConnectedNodes[i] < closestDist)
		{
		  closestDist = distanceFromConnectedNodes[i];
		  closestNode = i;
		}
	    }
	}
      //cerr << "Adding connection from " << lastConnection << " to " << closestNode << endl;
      sum += closestDist;
      lastConnection = closestNode;
      connected[closestNode] = true;
      ++numConnected;
    }
  cout << setprecision(2) << fixed << sum << endl;
  
  return true;
}



void undergroundCables (istream& in)
{
  bool finished = false;
  while (!finished)
    {
      finished = !processDataSet(in);
    }
}

int main (int argc, char** argv)
{
  // Program should normally read from standard in. But
  // for debugging purposes, it is sometimes easier to
  // give a file name on the command line.
  if (argc > 1)
    {
      ifstream in (argv[1]);
      undergroundCables (in);
    }
  else
    undergroundCables(cin);
  
  return 0;
}