#include <iostream>
#include<bits/stdc++.h>
#define int long long
#define FIO ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
#define F first
#define S second
using namespace std;

void debug() {
#ifdef Debug
    freopen("in.txt","r",stdin);
    freopen("out.txt","w",stdout);
#endif
}
#define ld long double
#define pi acos(-1)
const ld eps = 1e-9;
using pType = long double;
struct point{
    pType X, Y;
    ld angle;

    point(){
        X = Y = angle = 0;
    };

    point(pType x, pType y){
        X = x, Y = y;

        if(Y == 0)
            angle = (X < 0 ? pi : 0);
        else if(X == 0)
            angle = (Y < 0 ? 3 * pi / 2 : pi / 2);

        angle = atan2(Y, X);
        if(X > 0 and Y > 0)
            ;
        else if(X < 0 and Y > 0)
            angle = pi - angle;
        else if(X < 0 and Y < 0)
            angle = pi + angle;
        else
            angle = 2 * pi - angle;
    }

    const point operator*(const ld &factor) const{
        return point(X * factor, Y * factor);
    }

    const point operator-(const point &other) const {
        return point(X - other.X, Y - other.Y);
    }

    const point operator+(const point &other) const {
        return point(X + other.X, Y + other.Y);
    }


};
ld dist(point a, point b){
    return sqrt(fabs(a.X - b.X) * fabs(a.X - b.X) + fabs(a.Y - b.Y) * fabs(a.Y - b.Y));
}

point vec(point a, point b){
    return b - a;
}

pType cross(point a, point b)
{
    return a.X * b.Y - a.Y * b.X;
}
pType dot(point a, point b){
    return a.X * b.X + a.Y * b.Y;
}
bool intersectSegments(point a, point b, point c, point d, point &intersect){
    ld d1 = cross(vec(b, a), vec(c, d)), d2 = cross(vec(c, a), vec(c, d)), d3 = cross(vec(b, a), vec(c, a));

    if (fabs(d1) < eps)
        return 0; /// parllel or identical

    ld t1 = d2 / d1, t2 = d3 / d1;
    intersect = a + (b - a) * t1;

    /// segment: [0, 1]
    /// ray: [0, INF]
    /// line: [-INF, INF]

    /// make sure that eps is not too accurate
    // if(t1 < -eps or t1 > 1 + eps or t2 < -eps or t2 > 1 + eps)
    //     return 0;

    return 1;
}
bool same(point a, point b){
    return dot(vec(a, b), vec(a, b)) == 0;
}
void getAnswer()
{
    int n;
    cin >> n;
    vector<pair<point,point>> v;
    for(int i = 0;i < n;++i)
    {
        int a,b,c,d;
        cin >> a >> b >> c >> d;
        point p1 (a,b);
        point p2 (c,d);
        v.push_back({p1,p2});
    }  
    ld maxi = 0;
    for(int i = 0;i < n;++i)
    {
        for(int j = i + 1;j < n;++j)
        {
            for(int k = j + 1;k < n;++k)
            {
                point a,b,c;
                if(intersectSegments(v[i].F, v[i].S, v[j].F, v[j].S, a)
                    and intersectSegments(v[j].F, v[j].S, v[k].F, v[k].S, b)
                    and intersectSegments(v[i].F, v[i].S, v[k].F, v[k].S, c) 
                    and !same(a,b) and !same(a,c) and !same(b,c))
                {
                    maxi = max(maxi, dist(a,b) + dist(b,c) + dist(a,c));
                }
            }
        }
    }
    if(maxi == 0)
        cout << "no triangle\n";
    else
        cout << fixed << setprecision(12) << maxi;
}       
signed main() 
{
    FIO
    debug();
    int t = 1;
    //cin >> t;
    while(t--)
        getAnswer();
    return 0;

}