#include <bits/stdc++.h>
using namespace std;

#define zedanov                   \
    ios_base::sync_with_stdio(0); \
    cin.tie(0);                   \
    cout.tie(0);
#define ld long double
#define el "\n"
const int N = 1e5 + 5, md = 1e9 + 7;
ld inf = LDBL_MAX;
// Verify Logic, Check Constrains
// Overflow, Fits in Time/Memory ?

struct point
{
    ld x, y;
    double dist(const point &other)
    {
        abs(sqrtl((x - other.x) * (x - other.x) + (y - other.y) * (y - other.y)));
    }
};
struct line
{
    ld m, c;
    point intersect(const line &other)
    {
        ld x, y;
        if (m == other.m)
            return {inf, inf};
        x = (other.c - c) / (m - other.m);
        y = m * x + c;
        return {x, y};
    }
};

void doWork()
{
    int n;
    cin >> n;
    vector<line> a(n);
    for (int i = 0; i < n; i++)
    {
        double x1, y1, x2, y2;
        cin >> x1 >> y1 >> x2 >> y2;
        if (x1 == x2)
        {
            a[i].m = inf;
            a[i].c = x1;
        }
        else if (y1 == y2)
        {
            a[i].m = 0;
            a[i].c = y1;
        }
        else
        {
            a[i].m = (y2 - y1) / (x2 - x1);
            a[i].c = y1 - a[i].m * x1;
        }
    }
    double ans = 0;
    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < n; j++)
        {
            if (i == j)
                continue;
            for (int k = 0; k < n; k++)
            {
                if (i == k || j == k)
                    continue;
                auto p1 = a[i].intersect(a[j]);
                auto p2 = a[i].intersect(a[k]);
                auto p3 = a[j].intersect(a[k]);
                if (p1.x == inf || p2.x == inf || p3.x == inf)
                    continue;
                ans = max(ans, p1.dist(p2) + p1.dist(p3) + p2.dist(p3));
            }
        }
    }
    if (ans > 0)
        cout << fixed << setprecision(8) << ans;
    else
        cout << "no triangle";
}

signed main()
{
    zedanov int t = 1;
    // cin >> t;
    while (t--)
        doWork();

    return 0;
}