#include <bits/stdc++.h>

using namespace std;

#define speed ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define pb push_back
#define mp make_pair
#define F first
#define S second
#define sz(x) (int)(x.size())
#define all(x) x.begin(), x.end()

typedef long long ll;
typedef unsigned long long ull;


const ll INF = LLONG_MAX;
const int inf = INT_MAX;
const int N = 5005;
const ll MOD = 1e9+7;
const double EPS = 1e-9;

short int p[N], r[N];

void make_set(short int v){
    p[v] = v;
    r[v] = 1;
}

short int find_set(short int v){
    if(p[v] == v)
        return v;
    return p[v] = find_set(p[v]);
}

void union_sets(short int u, short int v){
    u = find_set(u);
    v = find_set(v);
    if(u == v)
        return;
    if(r[u] < r[v])
        swap(u, v);
    p[v] = u;
    if(r[u] == r[v])
        r[u]++;
}

struct edge{
    short int u, v;
    int w;
};

struct cor{
    short int x, y;
};

bool cmp(edge a, edge b){
    return a.w < b.w;
}


vector <edge> edges;
vector <cor> c;

void solve(){
    short int n, x, y;
    double ans = 0;
    cin >> n;

    for(short int i = 1; i <= n; i++)
        make_set(i);

    for(short int i = 1; i <= n; i++){
        cin >> x >> y;
        c.pb({x, y});
    }

    for(short int i = 0; i < n; i++)
        for(short int j = i+1; j < n; j++)
            edges.pb({i + 1, j + 1, (int)(c[i].x - c[j].x) * (int)(c[i].x - c[j].x) + (int)(c[i].y-c[j].y) * (int)(c[i].y-c[j].y)});

    sort(all(edges), cmp);

    for(auto x : edges){
        if(find_set(x.u) != find_set(x.v)){
            union_sets(x.u, x.v);
            ans += sqrt(x.w);
        }
    }
    cout << fixed << setprecision(6) << '\n';;
    cout << ans << '\n';
}

int main(){
    speed;

    freopen("unionday.in","r",stdin);
    freopen("unionday.out","w",stdout);

    int T = 1;


    while(T--)
        solve();

    return 0;
}