#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>    // 包含 tree、gp_hash_table、cc_hash_table
#include <ext/pb_ds/priority_queue.hpp> // 引入后使用 STL 的堆需要 std::
#include <ext/rope>
using namespace __gnu_pbds;
using namespace __gnu_cxx;
using namespace std;
template<class key, class val = null_type, class cmp = less<>>
using rb_tree = tree<key, val, cmp, rb_tree_tag, tree_order_statistics_node_update>;
template<class key, class cmp = less<>>
using pairing_heap = __gnu_pbds::priority_queue<key, cmp>;
typedef long long ll;
#define int long long
mt19937_64 rd(time(0));

using type = double;
struct point : array<type, 3> {
    point operator * (const point & t) const { return {at(1) * t[2] - at(2) * t[1], at(2) * t[0] - at(0) * t[2], at(0) * t[1] - at(1) * t[0]}; }
    type operator / (const point & t) const { return at(0) * t[0] + at(1) * t[1] + at(2) * t[2]; }
    point & operator += (const point & t) { return at(0) += t[0], at(1) += t[1], at(2) += t[2], *this; }
    point operator + (const point & t) const { return point(*this) += t; }
    point & operator -= (const point & t) { return at(0) -= t[0], at(1) -= t[1], at(2) -= t[2], *this; }
    point operator - (const point & t) const { return point(*this) -= t; }
    point & operator *= (const type & t) { return at(0) *= t, at(1) *= t, at(2) *= t, *this; }
    point operator * (const type & t) const { return point(*this) *= t; }
    point & operator /= (const type & t) { return at(0) /= t, at(1) /= t, at(2) /= t, *this; }
    point operator / (const type & t) const { return point(*this) /= t; }

    void shake(double eps = 1e-10) {
        for (auto & t : *this) {
            t += ((double)rand() / RAND_MAX - 0.5) * eps;
        }
    }
};

struct face {
    array<int, 3> v;
    point norm;
};

vector<face> hull(vector<point> & q, vector<face> res = {}) {
    res.emplace_back(face{0, 1, 2, (q[1] - q[0]) * (q[2] - q[0])});
    res.emplace_back(face{2, 1, 0, (q[1] - q[2]) * (q[0] - q[2])});

    for (int i = 3; i < q.size(); i++) {
        vector<face> nf;
        set<array<int, 2>> edge;
        for (auto & x : res) {
            auto & [a, b, c] = x.v;
            if ((q[b] - q[a]) * (q[c] - q[a]) / (q[i] - q[a]) > 0) {
                edge.emplace(array<int, 2>{a, b});
                edge.emplace(array<int, 2>{b, c});
                edge.emplace(array<int, 2>{c, a});
            } else {
                nf.emplace_back(face{a, b, c, (q[b] - q[a]) * (q[c] - q[a])});
            }
        }
        for (auto & [x, y] : edge) {
            if (edge.count({y, x})) continue;
            nf.emplace_back(face{x, y, i, (q[y] - q[x]) * (q[i] - q[x])});
        }
        swap(res, nf);
    }
    return res;
}

void output(__int128 x) {
    if(x < 10) {
        cout << (int)x;
        return;
    }
    output(x / 10);
    cout << (int) (x % 10);
}

void QAQ() {
    int n;
    cin >> n;

    vector<point> q(n);

    for (int i = 0; i < n; i++) {
        cin >> q[i][0] >> q[i][1] >> q[i][2];
        q[i].shake();
    }

    auto res = hull(q);

    double ans = 0;

    for (auto & x : res) {
        ans += sqrt(x.norm / x.norm);
    }

    cout << ans / 2 << "\n";
}

signed main() {
    cin.tie(0) -> sync_with_stdio(0);
    cout << fixed << setprecision(3);
    int t = 1;
    // cin >> t;

    while (t--) {
        QAQ();
    }
}