// An AC a day keeps the doctor away.
#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
#ifdef local
#define safe std::cerr<<__PRETTY_FUNCTION__<<" line "<<__LINE__<<" safe\n"
#define debug(args...) qqbx(#args, args)
#define orange(args...) danb(#args, args)
using std::cerr;
template <typename ...T> void qqbx(const char *s, T ...args) {
    int cnt = sizeof...(T);
    ((cerr << "\e[1;32m(" << s << ") = ("), ..., (cerr << args << (--cnt ? ", " : ")\e[0m\n")));
}
template <typename I> void danb(const char *s, I L, I R) {
    cerr << "\e[1;32m[ " << s << " ] = [ ";
    for (int f = 0; L != R; ++L) cerr << (f++ ? ", " : "") << *L;
    cerr << " ]\e[0m\n";
}
#else
#define safe ((void)0)
#define debug(...) ((void)0)
#define orange(...) ((void)0)
#endif // local
#define all(v) begin(v),end(v)

using namespace std;

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int n;
    cin >> n;

    map<pair<pair<int,int>,pair<int,int>>, int> mp;
    const auto readpt = []() {
        int x, y;
        cin >> x >> y;
        return make_pair(x, y);
    };

    vector<vector<int>> g(n);
    vector<int64_t> a(n);

    for (int i = 0; i < n; i++) {
        pair<int,int> p[3];
        for (int j = 0; j < 3; j++)
            p[j] = readpt();

        {
            complex<int64_t> c[3];
            for (int j = 0; j < 3; j++) {
                c[j] = {p[j].first, p[j].second};
            }
            a[i] = abs(imag(conj(c[2] - c[0]) * (c[1] - c[0])));
            debug(a[i]);
        }

        for (int j = 0; j < 3; j++) {
            auto e = make_pair(p[j], p[(j + 1) % 3]);
            if (e.first > e.second) swap(e.first, e.second);
            if (auto it = mp.find(e); it != mp.end()) {
                int x = it->second;
                g[i].emplace_back(x);
                g[x].emplace_back(i);
                debug(i, x);
            } else {
                mp[e] = i;
            }
        }
    }

    const auto dfs = [&](auto self, int i, int f = -1) -> pair<int64_t,int64_t> {
        // F = not take me, S = take me
        int64_t F = 0, S = a[i];
        if (g[i].size() != 3)
            F = 1e18;
        for (int j: g[i]) {
            if (j == f) continue;
            auto [sF, sS] = self(self, j, i);
            S += min(sF, sS);
            F += sS;
        }
        return {F, S};
    };

    auto [F, S] = dfs(dfs, 0);
    int64_t ans = min(F, S);
    cout << ans/2 << '.' << (ans%2==1 ? '5' : '0') << '\n';

    return 0;
}