#include <bits/stdc++.h>
using namespace std;
struct line{
    long double x1,y1;
    long double m=1e18,c;
    bool isVer = 0;
};
struct point{
    long double x,y;
};
point calc(line a, line b)
{
    point ret;
    if(a.isVer)
    {
        ret.x = a.x1;
        ret.y = a.x1 * b.m + b.c;
    }
    else if(b.isVer)
    {
        ret.x = b.x1;
        ret.y = b.x1 * a.m + a.c;
    }
    else
    {
        ret.x = (b.c - a.c) / (a.m - b.m);
        ret.y = a.m * ret.x + a.c;
    }
    return ret;
}
long double dist(point a, point b)
{
    return sqrt((a.x - b.x) * (a.x - b.x) + (a.y - b.y) * (a.y - b.y));
}
signed main(){

    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    int n;
    cin >> n;

    line lines[n];

    for(int i = 0; i < n; i++)
    {
        long double x1, y1, x2, y2;
        cin >> x1 >> y1 >> x2 >> y2;

        lines[i].x1 = x1;
        lines[i].y1 = y1;

        if(x1 == x2)
        {
            lines[i].isVer = 1;
            lines[i].m = 1e18;
            continue;
        }

        lines[i].m = (y2 - y1) / (x2 - x1);
        lines[i].c = -lines[i].m * x1 + y1;
    }

    long double ans = 0;

    for(int a = 0; a < n; a++)
    {
        for(int b = a + 1; b < n; b++)
        {
            for(int c = b + 1; c < n; c++)
            {
                
                set<int> s;
                s.insert(lines[a].m);
                s.insert(lines[b].m);
                s.insert(lines[c].m);
                if(s.size() != 3)
                    continue;

                point ab = calc(lines[a], lines[b]);
                point bc = calc(lines[b], lines[c]);
                point ca = calc(lines[a], lines[c]);

                long double tdist = dist(ab, bc) + dist(bc, ca) + dist(ca, ab);

                ans = max(ans, tdist);

            }
        }
    }

    if(ans)
        cout << fixed << setprecision(10) << ans << '\n';
    else
        cout << "no triangle\n";

}