#include <cstdlib>
#include <cstring>
#include <cstdio>
#include <iostream>
#include <iomanip>
#include <sstream>
#include <cmath>
#include <vector>
#include <stack>
#include <algorithm>
using namespace std;

int main()
{
	int i, j, k;
	int stackNum = 0;
	int stackSize = 0;

	int numBuildings;
	int chosenBuilding;
	float Xcoord, Ycoord;
	float tempDis, maxDis, totDis;
	vector<float> X, Y;
	vector<int> in;
	vector< stack<int> > out;
	stack<int> tempStack;

	out.push_back(tempStack);
	out.push_back(tempStack);

	while(1)
	{
		cin >> numBuildings;
		if(numBuildings == 0){ break; }

		totDis = 0;

		for(i = 0; i < numBuildings; i++)
		{
			cin >> Xcoord >> Ycoord;
			X.push_back(Xcoord);
			Y.push_back(Ycoord);
			out[stackNum].push(i);
		}

		in.push_back(out[stackNum].top());
		out[stackNum].pop();

		for(i = 0; i < numBuildings-1; i++)
		{
			maxDis = -1;

			for(j = 0; j < in.size(); j++)
			{
				stackSize = out[stackNum].size();
				for(k = 0; k < stackSize; k++)
				{
					tempDis = sqrt(pow((X[in[j]] - X[out[stackNum].top()]), 2) 
						+ pow((Y[in[j]] - Y[out[stackNum].top()]), 2));

					if(tempDis < maxDis || maxDis == -1){ maxDis = tempDis; chosenBuilding = out[stackNum].top(); }

					if(stackNum == 0){ out[stackNum+1].push(out[stackNum].top()); out[stackNum].pop(); }
					else { out[stackNum-1].push(out[stackNum].top()); out[stackNum].pop(); }
				}
				if(stackNum == 0){ stackNum = 1; } else { stackNum = 0; }
			}

			totDis += maxDis;

			stackSize = out[stackNum].size();
			for(k = 0; k < stackSize; k++)
			{
				if(out[stackNum].top() == chosenBuilding){ in.push_back(out[stackNum].top()); out[stackNum].pop(); }
				else
				{
					if(stackNum == 0){ out[stackNum+1].push(out[stackNum].top()); out[stackNum].pop(); }
					else { out[stackNum-1].push(out[stackNum].top()); out[stackNum].pop(); }
				}
			}
			if(stackNum == 0){ stackNum = 1; } else { stackNum = 0; }	
		}

		cout << fixed << setprecision(2) << totDis << endl;

		while(!out[0].empty()){ out[0].pop(); }
		while(!out[1].empty()){ out[1].pop(); }
		in.clear();
		X.clear();
		Y.clear();
        }


	return 0;
}