#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;

using point = array<ld, 2>;
using line = array<point, 2>;

static const ld eps = 1e-13;

ld solve(const vector<point> &p){
    auto plus = [&](point p, point q)->point{
        return {p[0] + q[0], p[1] + q[1]};
    };
    auto minus = [&](point p, point q)->point{
        return {p[0] - q[0], p[1] - q[1]};
    };
    auto dot = [&](point p, point q)->ld{
        return p[0] * q[0] + p[1] * q[1];
    };
    auto mul = [&](ld c, point p)->point{
        return {p[0] * c, p[1] * c};
    };
    auto cross = [&](point p, point q)->ld{
        return p[0] * q[1] - p[1] * q[0];
    };
    auto inter = [&](line s, line t)->point{
        ld alpha = cross(minus(t[0], s[0]), t[1]) / cross(s[1], t[1]);
        return plus(s[0], mul(alpha, s[1]));
    };

    int n = p.size();
    vector<line> hps(n);
    for(int i=0;i<n;i++) hps[i] = {p[(i+1)%n], minus(p[i], p[(i+1)%n])};

    sort(hps.begin(), hps.end(), [&](line a, line b) { 
        ld aang = atan2l(a[1][1], a[1][0]), bang = atan2l(b[1][1], b[1][0]);
        if(aang != bang) return aang < bang;

        line c = line({point({0, 0}), point({a[1][1], a[1][0]})});
        ld cang = atan2l(c[1][1], c[1][0]);
        point A = inter(c, a), B = inter(c, b);

        point C = b[0];
        C[0] -= b[1][0] * 14124412;
        C[1] -= b[1][1] * 14124412;
        return cross(minus(B, C), minus(A, C)) > 0;
    });

    auto bad = [&](line l, line m, line n)->bool{
        auto s = cross(l[1], m[1]);
        if(abs(s) < eps) return false;
        auto p = cross(n[1], minus(plus(mul(s, l[0]), mul(cross(minus(m[0], l[0]), m[1]), l[1])), mul(s, n[0])));
        return s > 0 ? p <= eps : p >= -eps;
    };

    deque<line> dq;
    for(auto p: hps){
        if(!dq.empty() && abs(cross(dq.back()[1], p[1])) <= eps) continue;
        while((int)dq.size() >= 2 && bad(dq[(int)dq.size() - 2], dq.back(), p)) dq.pop_back();
        while((int)dq.size() >= 2 && bad(dq[0], dq[1], p)) dq.pop_front();
        if((int)dq.size() < 2 || !bad(dq.back(), p, dq.front())) dq.push_back(p);
    }

    if(dq.size() < 3) return 0;

    int N = dq.size();
    vector<point> np(N);
    for(int i=0;i<N;i++) np[i] = inter(dq[i], dq[(i+1)%N]);

    ld re = 0;
    for(int i=0;i<N;i++) re += cross(np[i], np[(i+1)%N]);
    return abs(re)/2;
}


int main(){
    cin.tie(0)->sync_with_stdio(0);
    cout << fixed << setprecision(15);
     
    int n; cin >> n;
    vector<point> p(n);
    for(auto &[x, y] : p) cin >> x >> y;
    cout << solve(p);
}