#include <bits/stdc++.h>
using namespace std;
 
// Holi c:
 
#define ll long long int
#define fi first
#define se second
#define pb push_back
#define all(v) v.begin(), v.end()
 
const int Inf = 1e9;
const ll mod = 1e9+7;
const ll INF = 4e18;
 
using ld = long double;
const ld eps = 1e-6, inf = numeric_limits<ld>::max(), pi = acos(-1);
bool geq(ld a, ld b){return a-b >= -eps;}
bool leq(ld a, ld b){return b-a >= -eps;}
bool ge(ld a, ld b){return a-b > eps;}
bool le(ld a, ld b){return b-a > eps;}
bool eq(ld a, ld b){return abs(a-b) <= eps;}
bool neq(ld a, ld b){return abs(a-b) > eps;}

struct point{
	ld x, y;
	point(): x(0), y(0){}
	point(ld x, ld y): x(x), y(y){}

	point operator+(const point & p) const{return point(x + p.x, y + p.y);}
	point operator-(const point & p) const{return point(x - p.x, y - p.y);}
	point operator*(const ld & k) const{return point(x * k, y * k);}
	point operator/(const ld & k) const{return point(x / k, y / k);}

	point operator+=(const point & p){*this = *this + p; return *this;}
	point operator-=(const point & p){*this = *this - p; return *this;}
	point operator*=(const ld & p){*this = *this * p; return *this;}
	point operator/=(const ld & p){*this = *this / p; return *this;}

	point rotate(const ld & a) const{return point(x*cos(a) - y*sin(a), x*sin(a) + y*cos(a));}
	point perp() const{return point(-y, x);}
	ld ang() const{
		ld a = atan2l(y, x); a += le(a, 0) ? 2*pi : 0; return a;
	}
	ld dot(const point & p) const{return x * p.x + y * p.y;}
	ld cross(const point & p) const{return x * p.y - y * p.x;}
	ld norm() const{return x * x + y * y;}
	ld length() const{return sqrtl(x * x + y * y);}
	point unit() const{return (*this) / length();}

	bool operator==(const point & p) const{return eq(x, p.x) && eq(y, p.y);}
	bool operator!=(const point & p) const{return !(*this == p);}
	bool operator<(const point & p) const{return le(x, p.x) || (eq(x, p.x) && le(y, p.y));}
	bool operator>(const point & p) const{return ge(x, p.x) || (eq(x, p.x) && ge(y, p.y));}
	bool half(const point & p) const{return le(p.cross(*this), 0) || (eq(p.cross(*this), 0) && le(p.dot(*this), 0));}
};

istream &operator>>(istream &is, point & p){return is >> p.x >> p.y;}
ostream &operator<<(ostream &os, const point & p){return os << "(" << p.x << ", " << p.y << ")";}

int sgn(ld x){
	if(ge(x, 0)) return 1;
	if(le(x, 0)) return -1;
	return 0;
}

point intersectLines(const point & a1, const point & v1, const point & a2, const point & v2){
	//lines a1+tv1, a2+tv2
	//assuming that they intersect
	ld det = v1.cross(v2);
	return a1 + v1 * ((a2 - a1).cross(v2) / det);
}

int intersectLineSegmentInfo(const point & a, const point & v, const point & c, const point & d){
	//line a+tv, segment cd
	point v2 = d - c;
	ld det = v.cross(v2);
	if(eq(det, 0)){
		if(eq((c - a).cross(v), 0)){
			return -1; //infinity points
		}else{
			return 0; //no point
		}
	}else{
		return sgn(v.cross(c - a)) != sgn(v.cross(d - a)); //1: single point, 0: no point
	}
}

vector<point> cutPolygon(const vector<point> & P, const point & a, const point & v){
	//returns the part of the convex polygon P on the left side of line a+tv
	int n = P.size();
	vector<point> lhs;
	for(int i = 0; i < n; ++i){
		if(geq(v.cross(P[i] - a), 0)){
			lhs.push_back(P[i]);
		}
		if(intersectLineSegmentInfo(a, v, P[i], P[(i+1)%n]) == 1){
			point p = intersectLines(a, v, P[i], P[(i+1)%n] - P[i]);
			if(p != P[i] && p != P[(i+1)%n]){
				lhs.push_back(p);
			}
		}
	}
	return lhs;
}

vector<point> convexHull(vector<point> P){
	sort(P.begin(), P.end());
	vector<point> L, U;
	for(int i = 0; i < P.size(); i++){
		while(L.size() >= 2 && leq((L[L.size() - 2] - P[i]).cross(L[L.size() - 1] - P[i]), 0)){
			L.pop_back();
		}
		L.push_back(P[i]);
	}
	for(int i = P.size() - 1; i >= 0; i--){
		while(U.size() >= 2 && leq((U[U.size() - 2] - P[i]).cross(U[U.size() - 1] - P[i]), 0)){
			U.pop_back();
		}
		U.push_back(P[i]);
	}
	L.pop_back();
	U.pop_back();
	L.insert(L.end(), U.begin(), U.end());
	return L;
}

vector<point> funPolygon(vector<point> P, int i1){
    int n = P.size();
    vector<point> res, ans;
    set<point> aux;
    res.pb(P[i1]); aux.insert(P[i1]); res.pb(P[(i1 + 1) % n]); aux.insert(P[(i1 + 1) % n]);
    int i = (i1 + 2) % n;
    bool fl = false;
    while(1){
        int k = res.size();
        if(!fl){
            if(aux.find(P[i]) != aux.end() && i != i1){
                bool fla = false;
                for(int j = 0; j < k; j++){
                    if(res[j] == P[i]) fla = true;
                    if(fla) ans.pb(res[j]);
                }
                break;
            }
            if(geq((res[k - 1] - res[k - 2]).cross(P[i] - res[k - 2]), 0)){
                res.pb(P[i]); aux.insert(P[i]);
                i = (i + 1) % n;
            }else{
                fl = true;
            }
        }else{
            auto u = intersectLineSegmentInfo(res[k - 2], res[k - 1] - res[k - 2], P[i], P[(i + 1) % n]);
            if(u == 1){
                auto it = intersectLines(res[k - 2], res[k - 1] - res[k - 2], P[i], P[(i + 1) % n] - P[i]);
                if(it != P[(i + 1) % n]){
                    if(it == P[i]) res.pb(P[i]), aux.insert(P[i]);
                    else res.pb(it), aux.insert(it);
                    fl = false;
                }
            }else if(u == -1){
                res.pb(P[i]); aux.insert(P[i]);
                fl = false;
            }
            i = (i + 1) % n;
        }
    }
    ans = convexHull(ans);
    return ans;
}

vector<point> intersectPolygons(vector<point> A, vector<point> B){
    int n = B.size();
    for(int i = 0; i < n; i++){
        A = cutPolygon(A, B[i], B[(i + 1) % n] - B[i]);
    }
    return A;
}

ld area(vector<point> & P){
	int n = P.size();
	ld ans = 0;
	for(int i = 0; i < n; i++){
		ans += P[i].cross(P[(i + 1) % n]);
	}
	return abs(ans / 2);
}

int main(){
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    int n; cin>>n;
	vector<point> P(n);
	for(int i = 0; i < n; i++){
		int a, b; cin>>a>>b;
		P[i] = point(a, b);
	}
    vector<vector<point>> Ps;
    for(int i = 0; i < n; i++){
        auto v = funPolygon(P, i);
        //cout<<P[i]<<" -> ";
        //for(auto d : v) cout<<d<<" "; cout<<'\n';
        if(v.size() > 2) Ps.pb(v);
    }
    sort(all(Ps));
    Ps.erase(unique(all(Ps)), Ps.end());
    for(auto d : Ps){
        //for(auto e : d) cout<<e<<" ";
        //cout<<area(d);
        //cout<<'\n';
    }
    auto ans = Ps[0];
    for(int i = 1; i < Ps.size(); i++){
        ans = intersectPolygons(ans, Ps[i]);
    }
    if(n > 100 && eq(area(ans), area(P))) cout<<"E";
    cout<<setprecision(25)<<area(ans);
}