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#include<bits/stdc++.h>
using namespace std;
typedef long double lf;

struct Point{
	lf x,y;

	Point(void) {}
	Point(lf x, lf y): x(x), y(y) {}
};

istream& operator >> (istream& s, Point& a){
	s >> a.x >> a.y;
	return s;
}

ostream& operator << (ostream& s, const Point& a){
	s << "(" << setw(6) << a.x << ", " << setw(6) << a.y << ")";
	return s;
}

struct Line{
	lf a,b,c;
	Line(void) {}
	Line(const Point& x, const Point& y){
		a = y.x - x.x;
		b = x.y - y.y;
		c = x.x*y.y - x.y*y.x;
	}
};

lf det(const Point& a, const Point& b, const Point& c){
	return a.x*b.y + b.x*c.y + c.x*a.y - (a.y*b.x + b.y*c.x + c.y*a.x);
}

lf calcField(const vector<Point>& t){
	lf res = 0;
	for(int i=0;i<t.size();i++)
		res += det(t[0], t[i], t[(i+1)%t.size()])/2.0;
	return res;
}

int getSide(const Point& a, const Point& b, const Point& c){
	lf x = det(a,b,c);
	if(x < 0.0)
		return -1;
	return (x > 0.0 ? 1 : 0);
}

lf distance(const Point& a, const Point& b){
	return sqrt((a.x-b.x)*(a.x-b.x) + (a.y-b.y)*(a.y-b.y));
}

bool operator == (const Point& a, const Point& b){
	return (a.x == b.x) && (a.y == b.y);
}

Point c;
bool cmp(const Point& a, const Point& b){
	if(a == c)
		return true;
	if(b == c)
		return false;

	int x = getSide(c,a,b);
	return (x == 1) || (x == 0 && distance(c,a) < distance(c,b));
}

vector<Point> convexHull(vector<Point>& t){
	c = t[0];

	for(auto& i : t)
		if(i.y < c.y || (i.y == c.y && i.x < c.x))
			c = i;
	
	sort(t.begin(), t.end(), cmp);

	vector<Point> s;
	s.push_back(t[0]), s.push_back(t[1]);
	int n = s.size();

	for(int i=2;i<t.size();i++){
		while(n >= 2 && getSide(s[n-2], s[n-1], t[i]) != 1)
			s.pop_back(), n--;
		s.push_back(t[i]);
		n++;
	}

	return s;
}

Point intersect(const Point& a, const Point& b, const Point& x, const Point& y){
	Line p(a,b);
	Line q(x,y);

	lf k = p.b*q.c - p.c*q.b;
	lf l = p.c*q.a - p.a*q.c;
	lf m = p.a*q.b - p.b*q.a;

//	cout << "<<< " << l/m << " " << k/m << "\n";

	return Point(l/m, k/m);
}

vector<Point> intersect(vector<Point> a, vector<Point> b){
	vector<Point> res;
/*
	for(auto& i : b)
		cout << "$$ " << i << "\n";
	for(auto& i : a)
		cout << "## " << i << "\n";
	cout << "______________\n"; 
*/
	for(int i=0;i<a.size();i++){
		res.clear();
		Point x = a[i];
		Point y = a[(i+1)%a.size()];
//		cout << x << " " << y << "\n";

		for(int j=0;j<b.size();j++){
			Point p = b[j];
			Point q = b[(j+1)%b.size()];

			int k = getSide(x,y,p);
			int l = getSide(x,y,q);

//			cout << "====> " << p << " " << q << "\n";

			if(k >= 0 && l >= 0){
				res.push_back(q);
//				cout << "A\n";
			}else if(k > 0 && l <= 0){
				res.push_back(intersect(x,y,p,q));
//				cout << "B\n";
			}else if(k < 0 && l >= 0){
				res.push_back(intersect(x,y,p,q));
				res.push_back(q);
//				cout << "C\n";
			}
		}

		b = res;
//		for(auto& i : b)
//			cout << "---> " << i << "\n";
//		cout << "-----------------\n";
	}

	return res;
}

int main(void){
	ios_base::sync_with_stdio(false);
	cout << fixed << setprecision(9);

	int n;
	cin >> n;

	vector<pair<Point, Point> > t(n);
	for(auto& i : t)
		cin >> i.first >> i.second;

	vector<Point> res;
	bool ok=false;

	vector<Point> p;
	vector<Point> h;
	for(int i=0;i<(1<<n);i++){
		p.clear();
		for(int j=0;j<n;j++)
			if(i&(1<<j))
				p.push_back(t[j].first);
			else
				p.push_back(t[j].second);

		h = convexHull(p);

		if(!ok)
			res = p, ok = true;
		else
			res = intersect(res, p);
/*
		for(auto& i : res)
			cout << "############## " << i << "\n";
		cout << "-----------------\n";
*/	}

	cout << (res.size() == 0 ? 0.0 : calcField(res)) << "\n";

	return 0;
}