#include <bits/stdc++.h>
#define x first
#define y second
#define point pair<double,double>

using namespace std;
ofstream g("camera.out");
int n;
long double area;
long double sumx,sumy;
vector<point> p,r,p1;
int poz = 31999;
char buffer[32010];

void inc()
{
    ++poz;
    if(poz == 32000)
    {
        fread(buffer,1,32000,stdin);
        poz = 0;
    }
}

void read(int &x)
{
    char sign = '+';
    x = 0;
    while(buffer[poz] < '0' || buffer[poz] > '9')
    {
        sign = buffer[poz];
        inc();
    }
    while(buffer[poz] >= '0' && buffer[poz] <= '9')
    {
        x = x * 10 + buffer[poz] - '0';
        inc();
    }
    if(sign == '-')
        x = -x;
}

bool exist(point po1)
{
    for(int i = 0;i <p1.size();++i)
        if(p[i].x == po1.x && p[i].y == po1.y)
            return true;
    return false;
}

bool cmp(point po1,point po2)
{
    return atan2(po1.x - sumx / n,po1.y - sumy / n) > atan2(po2.x - sumx / n,po2.y - sumy / n);
}

bool cmp1(point po1,point po2)
{
    return atan2(po1.x - sumx / r.size(),po1.y - sumy / r.size()) > atan2(po2.x - sumx / r.size(),po2.y - sumy / r.size());
}

void Read()
{
    freopen("camera.in","r",stdin);
    int x,y;
    read(n);
    for(int i=1;i<=n;++i)
    {
        read(x);
        read(y);
        sumx += x;
        sumy += y;
        p.push_back(make_pair(x,y));
    }
    fclose(stdin);
    sort(p.begin(),p.end(),cmp);
    p.push_back(p[0]);
    p1 = p;
}


point intersection(point po1,point po2,point po3,point po4)
{
    double x1 = po1.y - po2.y;
    double y1 = po2.x - po1.x;
    double c1 = po1.x * po2.y - po2.x * po1.y;
    double x2 = po3.y - po4.y;
    double y2 = po4.x - po3.x;
    double c2 = po3.x * po4.y - po4.x * po3.y;

    double x = (y1 * c2 - y2 * c1) / (x1 * y2 - x2 * y1);
    double y = (c2 * x1 - c1 * x2) / (y1 * x2 - y2 * x1);

    return {x , y};
}

int cross_product(point po1,point po2,point po3)
{
    return (po2.y - po3.y) * (po1.x - po3.x) - (po1.y - po3.y) * (po2.x - po3.x);
}

void intersection_points()
{
    for(int i = 0;i < p.size() - 3;++i)
        for(int j = i + 2;j < p.size();++j)
        {
            point result = intersection(p[i],p[i+1],p[j],p[j+1]);
            if(!exist(result) && result.x <= 200000 && result.y <= 200000)
                p1.push_back(result);
        }
}

void Solve()
{
    for(int i = 0;i < p.size() - 1;++i)
    {
        r.clear();

        for(int j = 0;j < p1.size();++j)
        {
            point curr = p1[j];
            if(cross_product(p[i],p[i + 1],curr) >= 0)
                r.push_back(curr);
        }

        p1.clear();
        p1 = r;
    }
}

void calculate_area()
{
    sumx = sumy = 0;
    for(int i=0;i<r.size();++i)
    {
        sumx += r[i].x;
        sumy += r[i].y;
    }
    r.push_back(r[0]);
    for(int i = 0;i < r.size() - 1;++i)
        area += r[i].x * r[i+1].y - r[i].y * r[i+1].x;
    if(area < 0)
        area = -area;
    area /= 2.0;
}

void Print()
{
    g<<setprecision(2)<<fixed;
    g<<area;
    g.close();
}

int main()
{
    Read();
    intersection_points();
    Solve();
    calculate_area();
    Print();
    return 0;
}