#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
using namespace std;
#define mp make_pair

vector<pair<int, int>> point;

double dist(int i1, int i2) {
    auto p1 = point[i1];
    auto p2 = point[i2];
    return sqrt((p1.first - p2.first)*(p1.first - p2.first) + (p1.second - p2.second)*(p1.second - p2.second));
}

vector<double> dst;

int main() {
    int n;
    cin >> n;
    dst.resize(n, 1e9);
    for (int i = 0; i < n; ++i) {
        int x, y;
        cin >> x >> y;
        point.emplace_back(x, y);
    }

    vector<bool> used(n,false);
    dst[0] = 0;
    for (;;) {
        int v = -1;
        for (int i = 0; i < n; ++i) {
            if (!used[i] && dst[i] < 1e9 && (v==-1 || dst[v] > dst[i])) {
                v = i;
            }
        }
        if (v==-1) break;
        used[v] = true;
        for (int i = 0; i < n; ++i) {
            if (!used[i]) {
                dst[i] = min(dst[i], dist(v,i));
            }
        }
    }

    double res =0;
    for(int i=0;i<n;++i) {
        res += dst[i];
    }
    printf("%.10f",res);
    return 0;
}