#include <bits/stdc++.h>
using namespace std;
typedef long long LL;

struct point
{
    LL x;
    LL y;
    point () {}
    point (LL x_, LL y_)
    {
        x = x_;
        y = y_;
    }
    void show()
    {
        cout << "(" << x << "," << y << ")\n";
    }
};

struct vect
{
    LL x;
    LL y;
    vect () {}
    vect (LL x_, LL y_)
    {
        x = x_;
        y = y_;
    }
    vect (point A, point B)
    {
        x = A.x - B.x;
        y = A.y - B.y;
    }
    void show()
    {
        cout << "(" << x << "," << y << ")\n";
    }
};

vector <point> Read()
{
    int n;
    cin >> n;
    vector <point> res(n);
    for (int i=0; i!=n; ++i) cin >> res[i].x >> res[i].y;
    return res;
}

LL vectCross (vect V, vect U)
{
    return V.x * U.y - V.y * U.x;
}

short det(point A, point B, point C)
{
    LL val = vectCross(vect(A,B), vect(A,C));
    if (val == 0) return 0; //na linii
    if (val > 0) return 1; //przeciwzegarowo
    if (val < 0) return -1; //zegarowo
}
point X;

LL distSQ (point A, point B)
{
    return (A.x-B.x)*(A.x-B.x) + (A.y-B.y)*(A.y-B.y);
}

bool polarCompare (const point &A, const point &B)
{
    short orient = det(X,A,B);
    if (orient == 0) return distSQ(X,A) < distSQ(X,B);
    return (orient == 1);
}

void PolarSort(vector <point> &data)
{
    int ind = 0;
    for (int i=0; i!=data.size(); i++)
    {
        if (data[i].y < data[ind].y) ind = i;
        else if (data[i].x < data[ind].x && data[i].y == data[ind].y) ind = i;
    }
    X = data[ind];
    swap(data[ind],data[0]);
    sort(data.begin()+1, data.end(), polarCompare);
}

bool FlatCmp (const point &A, const point &B)
{
    return (A.x < B.x || (A.x == B.x && A.y < B.y));
}

void Graham (vector <point> &data)
{
    int n = data.size();
    sort(data.begin(), data.end(), FlatCmp);

    vector <point> Top;
    for (int i=0; i<n; ++i)
    {
        while (Top.size() > 1 && det(Top[Top.size()-2], Top[Top.size()-1], data[i]) != -1) Top.pop_back();
        Top.push_back(data[i]);
    }

    vector <point> Bottom;
    for (int i=n-1; i>=0; --i)
    {
        while (Bottom.size() > 1 && det(Bottom[Bottom.size()-2], Bottom[Bottom.size()-1], data[i]) != -1) Bottom.pop_back();
        Bottom.push_back(data[i]);
    }

    data = Top;
    for (int i=1; i<Bottom.size()-1; ++i) data.push_back(Bottom[i]);
}

void CalcArea (vector <point> &K)
{
    LL res = 0;
    int j = K.size() - 1;
    for (int i=0; i<K.size(); ++i)
    {
        res += K[i].x * K[j].y;
        res -= K[i].y * K[j].x;
        j = i;
    }

    cout << (res >> 1);
    if (res%2) cout << ".500000";
    else cout << ".000000";

}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    vector <point> All = Read();
    Graham(All);
    CalcArea(All);
    return 0;
}