#include<bits/stdc++.h>
using namespace std;
#define db long double
const db eps=1e-12;
int sgn(db a){
	if(abs(a)<eps)return 0;
	return a>0?1:-1;
}
db p2(db x){return x*x;}
struct no{
	db x,y;
	no(){x=0,y=0;}
	no(db x_,db y_){x=x_,y=y_;}
	no operator + (const no &a) const{return no(x+a.x,y+a.y);}
	no operator - (const no &a) const{return no(x-a.x,y-a.y);}
	no operator * (const db &k) const{return no(x*k,y*k);}
	no operator / (const db &k) const{return no(x/k,y/k);}
	inline db dis(no a){return p2(x-a.x)+p2(y-a.y);}
	inline no rot(){return no(-y,x);}
};
db cro(no a,no b){return a.x*b.y-a.y*b.x;}
db sat(no a,no b,no c){return cro(b-a,c-a);}
struct ed{
	no s,t;db jm;
	ed(){}
	ed(no s_,no t_){s=s_,t=t_,jm=atan2(t.y-s.y,t.x-s.x);}
	inline int side(no a){return sgn(sat(s,t,a));}
	bool operator < (const ed &a) const{
		if(sgn(jm-a.jm)!=0)return jm<a.jm;
		return sgn(sat(a.s,a.t,s))>0;
	}
};
no jd(ed a,ed b){
	db S1=sat(a.s,a.t,b.s),S2=sat(a.s,a.t,b.t);
	return (b.t*S1-b.s*S2)/(S1-S2);
}
ed hf(no s,no t){
	no m=s+t;m=m/2;
	return ed(m,m+(t-s).rot());
}
bool ck(ed a,ed b,ed c){return a.side(jd(b,c))<0;}
int m,m_;
ed e[500010],e_[500010],q[500010];
int l,r;
void gethalf(){
	sort(e+1,e+m+1);
	m_=0;
	for(int i=1;i<=m;i++){
		if(m_&&!sgn(e_[m_].jm-e[i].jm))continue;
		e_[++m_]=e[i];
	}
	m=m_;for(int i=1;i<=m;i++)e[i]=e_[i];
	l=1,r=0;
	for(int i=1;i<=m;i++){
		while(l<r&&ck(e[i],q[r],q[r-1]))r--;
		q[++r]=e[i];
	}
	while(l<r&&ck(q[l],q[r-1],q[r]))r--;
	while(l<r&&ck(q[l+1],q[l],q[r]))l++;
}
no a[500010];
int main(){
	int n;scanf("%d",&n);
	db x,y;
	for(int i=1;i<=n;i++)scanf("%Lf%Lf",&x,&y),a[i]=no(x,y);
	for(int i=n;i;i--)e[++m]=ed(a[i%n+1],a[i]);
	gethalf();
	n=0;
	for(int i=l;i<r;i++)a[++n]=jd(q[i],q[i+1]);
	if(r-l>1)a[++n]=jd(q[r],q[l]);
	db ans=0;
	for(int i=1;i<=n;i++)ans+=cro(a[i],a[i%n+1]);
	return printf("%.10Lf",abs(ans)/2),0;
}