#include <vector>
#include <cmath>
#include <cstdlib>
#include <cstdio>

using namespace std;

const double EPS = 1e-9;

double roundZero(long double d) {
	return abs(d) < EPS ? 0.0 : d;
}

#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define trav(a, x) for(auto& a : x)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;

template <class T> int sgn(T x) { return (x > 0) - (x < 0); }
template<class T>
struct Point {
	typedef Point P;
	T x, y;
	explicit Point(T x=0, T y=0) : x(x), y(y) {}
	bool operator<(P p) const { return tie(x,y) < tie(p.x,p.y); }
	bool operator==(P p) const { return tie(x,y)==tie(p.x,p.y); }
	P operator+(P p) const { return P(x+p.x, y+p.y); }
	P operator-(P p) const { return P(x-p.x, y-p.y); }
	P operator*(T d) const { return P(x*d, y*d); }
	P operator/(T d) const { return P(x/d, y/d); }
	T dot(P p) const { return x*p.x + y*p.y; }
	T cross(P p) const { return x*p.y - y*p.x; }
	T cross(P a, P b) const { return (a-*this).cross(b-*this); }
	T dist2() const { return x*x + y*y; }
	double dist() const { return sqrt((double)dist2()); }
	// angle to x-axis in interval [-pi, pi]
	double angle() const { return atan2(y, x); }
	P unit() const { return *this/dist(); } // makes dist()=1
	P perp() const { return P(-y, x); } // rotates +90 degrees
	P normal() const { return perp().unit(); }
	// returns point rotated 'a' radians ccw around the origin
	P rotate(double a) const {
		return P(x*cos(a)-y*sin(a),x*sin(a)+y*cos(a)); }
};

/*
template<class P>
pair<int, P> lineInter(P s1, P e1, P s2, P e2) {
	auto d = roundZero((e1 - s1).cross(e2 - s2));
	if (d == 0) // if parallel
		return {-(roundZero(s1.cross(e1, s2)) == 0), P(0, 0)};
	auto p = s2.cross(e1, e2), q = s2.cross(e2, s1);
	return {1, (s1 * p + e1 * q) / d};
}
*/

template<class P>
pair<int, P> lineInter(P aa, P ab, P ba, P bb) {
	auto difv = ba-aa, av = ab-aa, bv = ba-bb;
	double d = roundZero(av.cross(bv)), fa = difv.cross(bv), fb = av.cross(difv);
	if (d == 0) // if parallel
		return {0, P(0, 0)};
	if (d < 0) {
		d = -d;
		fa = -fa;
		fb = -fb;
	}
	auto t = aa + (av * fa) / d;
	return {1, t};
}

typedef Point<long double> P;
vector<P> polygonCut(const vector<P>& poly, P s, P e) {
	vector<P> res;
	rep(i,0,sz(poly)) {
		P cur = poly[i], prev = i ? poly[i-1] : poly.back();
		bool side = roundZero(s.cross(e, cur)) < 0;
		if (side != (roundZero(s.cross(e, prev)) < 0)) {
			pair<int, P> li = lineInter(s, e, cur, prev);
			if (li.first) res.push_back(li.second);
		}
		if (side)
			res.push_back(cur);
	}
	return res;
}

template<class T>
T polygonArea2(vector<Point<T>>& v) {
	T a = v.back().cross(v[0]);
	rep(i,0,sz(v)-1) a += v[i].cross(v[i+1]);
	return a;
}

int main() {
	int n;
	scanf("%d", &n);
	int max = 0;
	vector<P> polygon;
	for(int i=0;i<n;i++) {
		int x, y;
		scanf("%d %d", &x, &y);
		polygon.push_back(P(x, y));
		if (x > max) max = x;
		if (y > max) max = y;
	}
	vector<P> current;
	current.push_back(P(0, 0));
	current.push_back(P(0, max));
	current.push_back(P(max, max));
	current.push_back(P(max, 0));
	for (int i = 0; i < n; i++) {
		current = polygonCut(current, polygon[i], polygon[(i+1) % n]);
	}
	fprintf(stderr, "Poly size: %lu\n", current.size());
	printf("%.9Lf\n", current.size() == 0 ? 0 : -polygonArea2(current) / 2.0);
	return 0;
}