#include <fstream>
#include <algorithm>
#include <cstring>
#include <iomanip>
#include <vector>

using namespace std;

ifstream fin("camera.in");
ofstream fout("camera.out");

const double eps = 1e-5;

struct Point {
	double x, y;
	Point() {}
	Point(double x, double y) {
		this->x = x;
		this->y = y;
	}
};

int n;

vector< pair<Point, Point> > edges;
vector<Point> polygon;

inline double det(const Point &a, const Point &b, const Point &c) {

	return (b.x - a.x)*(c.y - a.y) - (b.y - a.y)*(c.x - a.x);

}

inline int sign(double x) {

	if (x > -eps && x < eps)
		return 0;
	if (x > 0)
		return 1;
	return -1;

}

Point intersect(const Point &p1, const Point &p2, const Point &p3, const Point &p4) {

	double a1 = p2.y - p1.y;
	double b1 = p1.x - p2.x;
	double c1 = p2.x*p1.y - p1.x*p2.y;
	
	double a2 = p4.y - p3.y;
	double b2 = p3.x - p4.x;
	double c2 = p4.x*p3.y - p3.x*p4.y;

	double div = a1*b2 - a2*b1;
	double x = (b1*c2 - b2*c1) / div;
	double y = (a2*c1 - a1*c2) / div;

	return Point(x, y);

}

vector<Point> aux;
inline void cutPolygon(const Point &a, const Point &b) {

	aux.clear();

	for (unsigned int i = 0; i + 1 < polygon.size(); ++i) {

		if (sign(det(polygon[i], a, b)) * sign(det(polygon[i + 1], a, b)) < 0) {

			Point temp = intersect(polygon[i], polygon[i + 1], a, b);

			if (sign(det(polygon[i], a, b)) > 0) {
				aux.push_back(polygon[i]);
				aux.push_back(temp);
			}
			else {
				aux.push_back(temp);
				aux.push_back(polygon[i + 1]);
			}

			continue;

		}

		if (sign(det(polygon[i], a, b)) >= 0)
			aux.push_back(polygon[i]);

	}

	aux.push_back(aux[0]);

	polygon = aux;

}

int main() {

	fin >> n;

	Point p0, prev;
	fin >> p0.x >> p0.y;
	prev = p0;

	double maxX = p0.x, minX = p0.x;
	double maxY = p0.y, minY = p0.y;

	for (int i = 2; i <= n; ++i) {

		Point curr;
		fin >> curr.x >> curr.y;

		maxX = max(maxX, curr.x);
		minX = min(minX, curr.x);
		maxY = max(maxY, curr.y);
		minY = min(minY, curr.y);

		edges.push_back(make_pair(prev, curr));

		prev = curr;

	}

	edges.push_back(make_pair(prev, p0));

	double aria = 0;
	for (unsigned int i = 0; i < edges.size(); ++i)
		aria += det(Point(0, 0), edges[i].first, edges[i].second);

	if (aria < 0) {

		for (unsigned int i = 0; i < edges.size(); ++i)
			swap(edges[i].first, edges[i].second);
		for (int i = 0, j = edges.size() - 1; i < j; ++i, --j)
			swap(edges[i], edges[j]);

	}

	polygon.push_back(Point(minX, minY));
	polygon.push_back(Point(maxX, minY));
	polygon.push_back(Point(maxX, maxY));
	polygon.push_back(Point(minX, maxY));
	polygon.push_back(Point(minX, minY));

	for (unsigned int i = 0; i < edges.size(); ++i) {

		cutPolygon(edges[i].first, edges[i].second);

	}

	aria = 0;
	for (unsigned int i = 0; i + 1 < polygon.size(); ++i)
		aria += det(Point(0, 0), polygon[i], polygon[i + 1]);
	aria /= 2.0;

	if (aria < 0)
		aria = -aria;

	fout << setprecision(2) << fixed << aria << '\n';

	return 0;

}

//Trust me, I'm the Doctor!