#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>

#define el '\n'
#define FIO ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);

using namespace std;
using namespace __gnu_pbds;

typedef long long ll;
typedef long double ld;
typedef complex<ld> pt;
typedef unsigned long long ull;

template<typename T, typename X>
using hashTable = gp_hash_table<T, X>;
template<typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T>
using ordered_multiset = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;

// mt19937_64 for long long
mt19937 rng(std::chrono::system_clock::now().time_since_epoch().count());

#define x real()
#define y imag()

const int INF = 1e9;
const ld eps = 1e-8, pi = acos(-1);

int dcmp(ld a, ld b)
{
    // a == b : 0
    // a != b : != 0
    // a > b : 1
    // a < b : -1
    // a >= b : != -1
    // a <= b : != 1
    return fabs(a - b) <= eps ? 0 : a < b ? -1 : 1;
}

ld cross(pt a, pt b)
{
    return ((conj(a) * (b)).imag());
}

bool isCollinear(pt a, pt b, pt c)
{
    return dcmp(cross(b - a, c - a), 0) == 0;
}

pt lineLineIntersection(pt A, pt B, pt C, pt D)
{
    // Line AB represented as a1x + b1y = c1
    ld a1 = B.y - A.y;
    ld b1 = A.x - B.x;
    ld c1 = A.x * B.y - B.x * A.y;
    // Line CD represented as a2x + b2y = c2
    ld a2 = D.y - C.y;
    ld b2 = C.x - D.x;
    ld c2 = C.x * D.y - D.x * C.y;

    double determinant = a1 * b2 - a2 * b1;
    if(determinant == 0)
    {
        // Same line aka Rakbin fo2 b3d
        if(isCollinear(A, B, C) && isCollinear(A, B, D))
            return pt(INF, INF);

        // The lines are parallel.
        return pt(-INF, -INF);
    }
    else
    {
        ld X = (b2 * c1 - b1 * c2) / determinant;
        ld Y = (a1 * c2 - a2 * c1) / determinant;
        return pt(X, Y);
    }
}

ld solve(pt a, pt b, pt c)
{
    return abs(a - b) + abs(a - c) + abs(b - c);
}

bool check(pt A)
{
    if(A.x == INF && A.y == INF)
        return false;
    if(A.x == -INF && A.y == -INF)
        return false;
    return true;
}

void doWork()
{
    int n;
    cin >> n;
    vector<pair<pt, pt>> v;
    for(int i = 0, x1, y1, x2, y2; i < n; i++)
    {
        cin >> x1 >> y1 >> x2 >> y2;
        v.push_back({pt(x1, y1), pt(x2, y2)});
    }
    ld ans = -100;

    for(int i = 0; i < n; i++)
    {
        for(int j = i + 1; j < n; j++)
        {
            pt A = lineLineIntersection(v[i].first, v[i].second, v[j].first, v[j].second);
            if(!check(A))
                continue;
            for(int k = j + 1; j < n; j++)
            {
                pt B = lineLineIntersection(v[i].first, v[i].second, v[k].first, v[k].second);
                pt C = lineLineIntersection(v[j].first, v[j].second, v[k].first, v[k].second);

                if(!check(B) || !check(C) || isCollinear(A, B, C))
                    continue;
                ans = max(ans, solve(A, B, C));
            }
        }
    }
    if(ans < 0)
        cout << "no triangle";
    else
        cout << fixed << setprecision(12) << ans;
}

signed main()
{
    FIO
    int T = 1;
//    cin >> T;
    for(int i = 1; i <= T; i++)
        doWork();
}