#include <bits/stdc++.h>

using namespace std;

struct point {
    double x, y;
};

double dist(point t1, point t2) {
    return sqrt((t1.x - t2.x) * (t1.x - t2.x) + (t1.y - t2.y) * (t1.y - t2.y));
}

int main() {
    int n;
    cin >> n;
    double x1[n + 1], x2[n + 1], y1[n + 1], y2[n + 1];
    double k[n + 1], b[n + 1];
    double f[n + 1];
    double inf = 1e5;
    fill(f, f + 1 + n, inf);
    for(int i = 1; i <= n; i++) {
        cin >> x1[i] >> y1[i] >> x2[i] >> y2[i];
        if(x1[i] == x2[i]) {
            f[i] = x1[i];
            k[i] = inf;
            continue;
        }
        k[i] = (y2[i] - y1[i]) / (x2[i] - x1[i]);
        b[i] = (y1[i] - k[i] * x1[i]);
    }
    double ans = 0;
    for(int i = 1; i <= n; i++) {
        for(int j = i + 1; j <= n; j++) {
            for(int l = j + 1; l <= n; l++) {
                if(abs(k[i] - k[j]) <= 0.00001 || abs(k[i] - k[l]) <= 0.00001 || abs(k[j] - k[l]) <= 0.00001)
                    continue;
                point pt1, pt2, pt3;
                if(k[i] == inf)
                    pt1.x = f[i];
                else if(k[j] == inf)
                    pt1.x = f[j];
                else
                    pt1.x = (b[j] - b[i]) / (k[i] - k[j]);
                if(k[i] != inf)
                    pt1.y = k[i] * pt1.x + b[i];
                else pt1.y = k[j] * pt1.x + b[j];
                if(k[i] == inf)
                    pt2.x = f[i];
                else if(k[l] == inf)
                    pt2.x = f[l];
                else
                    pt2.x = (b[l] - b[i]) / (k[i] - k[l]);
                if(k[i] != inf)
                    pt2.y = k[i] * pt2.x + b[i];
                else pt2.y = k[l] * pt2.x + b[l];
                if(k[j] == inf)
                    pt3.x = f[j];
                else if(k[l] == inf)
                    pt3.x = f[l];
                else
                    pt3.x = (b[j] - b[l]) / (k[l] - k[j]);
                if(k[j] != inf)
                    pt3.y = k[j] * pt3.x + b[j];
                else pt3.y = k[l] * pt3.x + b[l];
                if(abs(pt1.x - pt2.x) <= 0.00001 && abs(pt1.y - pt2.y) <= 0.00001)
                    continue;
                double P = dist(pt1, pt2) + dist(pt2, pt3) + dist(pt1, pt3);
                if(P > ans)
                    ans = P;
            }
        }
    }
    if(ans == 0)
        cout << "no triangle";
    else cout << fixed << setprecision(6) << ans;
    return 0;
}