#include<bits/stdc++.h>
#define MOGA ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
typedef long long int ll;
typedef double ld;
using namespace std;
int n, t = 1, k;
struct point {
    ld a, b;
};
vector<point>v;
point equ(ld x, ld y, ld a, ld b) {
    point cur;
    if (x == a) {
        cur.a = LDBL_MAX;
        cur.b = x;
    }
    else {
        cur.a = (b - y) / (a - x);
        cur.b = y - cur.a * x;
    }
    return cur;
}
point inter(point a, point b) {
    if (a.a == b.a)
    {
        a.a = LDBL_MAX;
        return a;
    } 
    point x;
    x.a = (b.b - a.b) / (a.a - b.a);
    x.b = (x.a * a.a) + a.b;
    return x;
}
ld clc(point a, point b) {
    return abs(sqrtl((a.a - b.a) * (a.a - b.a) + (a.b - b.b) * (a.b - b.b)));
}
ld area(point a, point b, point c) {
    return clc(a, b) + clc(b, c) + clc(a, c);
}
void go() {
    cin >> n;
    for (int i = 0;i < n;i++) {
        ld x1, y1, x2, y2;
        cin >> x1 >> y1 >> x2 >> y2;
        v.push_back(equ(x1, y1, x2, y2));
    }
    ld ans = -1;
    for (int i = 0;i < n;i++) {
        for(int j = 0;j < n;j++) {
            if(i!=j)
            for (int k = 0;k < n;k++) {
                if (k != i && j != k) {
                    point f1 = inter(v[i], v[j]), f2 = inter(v[k], v[j]), f3 = inter(v[i], v[k]);
                    if (f1.a == LDBL_MAX || f2.a == LDBL_MAX || f3.a == LDBL_MAX)continue;
                    ans = max(ans, area(f1, f2, f3));
                }
            }
        }
    }
    if (ans > 0)
        cout << ans;
    else
        cout << "no triangle";
}
int main()
{
    MOGA
      //  cin >> t;
    for (int i = 1;i <= t;i++)
    {
        go();
        cout << '\n';
    }
    return 0;
}