#include <unordered_map>
#include <string>
#include <vector>
#include <iostream>
#include <set>
#include <queue>
#include "optimization.h"
#include <math.h>
#include <unordered_map>
#include <iomanip>

using namespace std;
struct town {
    int x;
    int y;
};




int main() {
    vector<tuple<double, int, int>> edges;
    cout.tie(0);
    cin.tie(0);
    ios_base::sync_with_stdio(0);
    int n = readInt();
//    cin >> n;
    vector<town> towns(n);
    vector<int> id(n);
    vector<vector<int>> sets(n);
    for (int i = 0; i < n; i++) {
//        cin >> towns[i].x >> towns[i].y;
        towns[i].x = readInt(); towns[i].y = readInt();
        id[i] = i;
        sets[i].push_back(i);
    }
    unordered_map<int, double> used_x;
    for (int i = 0; i < n; i++) {
        for (int j = i + 1; j < n; j++) {
            auto x1 = towns[i].x;
            auto y1 = towns[i].y;
            auto x2 = towns[j].x;
            auto y2 = towns[j].y;
            int x = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
            if (used_x[x] == 0) {
                used_x[x] = sqrt(x);
            }
            edges.emplace_back(used_x[x], i, j);
        }
    }
    double answer = 0;
    sort(edges.begin(), edges.end());
    for (auto[w, a, b]: edges) {
        if (id[a] == id[b]) {
            continue;
        }
        answer += w;

        int small = a;
        if (sets[id[a]].size() > sets[id[b]].size()) {
            small = b;
        }
        int big = a + b - small;
        for (int x: sets[id[small]]) {
            id[x] = id[big];
            sets[id[big]].push_back(x);
        }


    }
//    cout << std::setprecision(10) << answer;
    writeDouble(answer, 10);
}