//Stephen Siena
//CSE 40872 - Problem 22
//November 13, 2009

#include <iostream>
#include <iomanip>
#include <vector>
#include <cmath>

using namespace std;

double mst(vector<float>, vector<float>, int);

int main(){

  while(1){
    int nPoints;
    cin >> nPoints;

    if (nPoints == 0)
      break;

    vector<float> xCoords;
    vector<float> yCoords;

    for(int i = 0; i < nPoints; i++){
      float x, y;
      cin >> x;
      cin >> y;
      xCoords.push_back(x);
      yCoords.push_back(y);
    }

    double distance = mst(xCoords, yCoords, nPoints);
    
    cout << fixed;
    cout << setprecision(2);
    cout << distance << endl;

  }

  return 0;
}


double mst(vector<float> xCoords, vector<float> yCoords, int n){

  double totalDistance = 0;

  vector<bool> connected;
  bool completeTree = false;

  if (xCoords.size() < 2)
    return 0;

  connected.resize(n);
  connected[0] = true;
  for (int i = 1; i < n; i++){
    connected[i] = false;
  }

  while (!completeTree){

    double smallestDistance = -1;
    double tempDistance;
    int newPoint;
    for (int i = 0; i < n; i++){
      if (connected[i]){
	for (int j = 0; j < n; j++){
	  if (!connected[j]){
	    tempDistance = sqrt(pow(xCoords[i]-xCoords[j],2)+pow(yCoords[i]-yCoords[j],2));
	    if ((tempDistance < smallestDistance) || smallestDistance == -1){
	      smallestDistance = tempDistance;
	      newPoint = j;
	    }
	  }
	}
      }
    }

    totalDistance += smallestDistance;
    connected[newPoint] = true;

    completeTree = true;
    for (int i = 0; i < n; i++){
      if (!connected[i]){
	completeTree = false;
	break;
      }		
    }
  }

  return totalDistance;

}