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#include<bits/stdc++.h>
#define VAR(i,n) __typeof(n) i = (n)
#define loop(i,j,s) for(int i=j;i<s;i++)
#define loopback(i,j,s) for(int i=j;i>=s;i--)
#define foreach(i,c) for(VAR(i,(c).begin());i!=(c).end();i++)
#define pln( x ) cout << x << "\n"
#define ps( x ) cout << x << " "
#define entr cout << "\n"
#define pcnt(i) __builtin_popcount(i)
#define ll long long
#define pb push_back
#define mp make_pair
#define ff first
#define ss second
#define SIZE(c) (c).size()
#define ALL(c) (c).begin(), (c).end()
using namespace std;
typedef vector<int> VI;
const int INFTY=20000000;
const int MAX=110;
const int MOD=10000000;

void coutTab(int* tab,int n){
	loop(i,0,n){
		cout<<tab[i]<<" ";
	}
	cout<<"\n";
}
//------------------------------------------
struct Point{
	double x, y;
	double ang;
};
typedef pair<Point, Point> ppp;
typedef vector<Point> vp;
vector<ppp> pps(MAX);
int n;
double prodVec(Point p0,Point p1, Point p2){
	return (p1.x-p0.x)*(p2.y-p0.y)-(p1.y-p0.y)*(p2.x-p0.x);
}
vp convexHull(vp ps){
	if(SIZE(ps)<2) return ps;
	int bi = 0;
	loop(i,1,SIZE(ps)){
		if((ps[i].y==ps[bi].y&&ps[i].x<ps[bi].y)||ps[i].y<ps[bi].y){
			bi = i;
		}
	}
	swap(ps[bi],ps[0]);
	Point bp = ps[0];
	loop(i,0,SIZE(ps)){
		ps[i].x-=bp.x;
		ps[i].y-=bp.y;
	}
	loop(i,1,SIZE(ps)){
		ps[i].ang = (double)ps[i].x/(ps[i].x*ps[i].x+ps[i].y*ps[i].y);
	}
	sort(ps.begin()+1,ps.end(), [](Point a, Point b){
		return a.ang>b.ang;
	});
	stack<Point> S;
	S.push(ps[0]);
	S.push(ps[1]);
	loop(i,2,SIZE(ps)){
		Point v = S.top();
		S.pop();
		Point r = S.top();
		S.pop();
		while(!S.empty()&&prodVec(r,v,ps[i])>=0){
			v=r;
			r=S.top();
			S.pop();
		}
		S.push(r);
		S.push(v);
		S.push(ps[i]);
	}
	vp res;
	while(!S.empty()){
		res.pb(S.top());
		S.pop();
	}
	loop(i,0,SIZE(res)){
		res[i].x+=bp.x;
		res[i].y+=bp.y;
	}
	reverse(ALL(res));
	return res;
}
bool inPol(vp pol, Point p){
	pol = convexHull(pol);
	loop(i,0,SIZE(pol)){
		if(prodVec(pol[i],pol[(i+1)%SIZE(pol)],p)>0) return false;
	}
	return true;
}
bool intLin(Point p1, Point p2, Point p3, Point p4){
	if(prodVec(p1,p2,p3)*prodVec(p1,p2,p4)<0 && prodVec(p3,p4,p1)*prodVec(p3,p4,p2)<0)
		return true;
	return false;	
}
vp intPol(vp pol1, vp pol2){
	vp res;
	loop(i,0,SIZE(pol1)){
		if(inPol(pol2,pol1[i])) res.pb(pol1[i]);
	}
	loop(i,0,SIZE(pol2)){
		if(inPol(pol1,pol2[i])) res.pb(pol2[i]);
	}
	loop(i,0,SIZE(pol1)){
		loop(j,0,SIZE(pol2)){
			Point pi1 = pol1[i];
			Point pi2 = pol1[(i+1)%SIZE(pol1)];
			Point pj1 = pol2[j];
			Point pj2 = pol2[(j+1)%SIZE(pol2)];
			if(intLin(pi1,pi2,pj1,pj2)){
				//ps(pi1.x);ps(pi2.x);pln("przeciecie");
				double a1 = (double)(pi2.y-pi1.y)/(pi2.x-pi1.x);
				double b1 = pi2.y-a1*pi2.x;
				double a2 = (double)(pj2.y-pj1.y)/(pj2.x-pj1.x);
				double b2 = pj2.y-a1*pj2.x; 
				Point inte;
				inte.x = (b2-b1)/(a1-a2);
				inte.y = a1*inte.x+b1;
				res.pb(inte);
			}
		}
	}
	for(auto r : res){
	//	ps(r.x);pln(r.y);
	}
	return res;
}
double field(vp pol){
	double res=0;
	pol = convexHull(pol);
	loop(i,1,SIZE(pol)){
		res += abs(prodVec(pol[0],pol[i],pol[(i+1)%SIZE(pol)]))/2.0;
	}
	return res;
}
int main(){
	ios_base::sync_with_stdio(0);
	cin>>n;
	loop(i,0,n){
		cin>>pps[i].ff.x>>pps[i].ff.y>>pps[i].ss.x>>pps[i].ss.y;
	}
	vp ps,res;
	loop(mask, 0, 1<<n){
		ps.clear(); 
		loop(j,0,n){
			if(1<<j&mask){
				ps.pb(pps[j].ss);
			}else{
				ps.pb(pps[j].ff);
			}
		}
		vp hulled = convexHull(ps);
		if(mask == 0) res = hulled;
		else res = intPol(res,hulled);
	}
	pln(field(res));
}