#include<bits/stdc++.h>
using namespace std;
#define L long long
#define D double
#define P pair<D,D>

D integ(D x, D d) {
    return x*(1+1/(d-1)) - x * x * x / (3 * (d - 1));
}

D calcSol(D w, D h) {
    double res = -1;
    for (int i = 0; i < 2; i++) {
        double c = (1 + 1 / (h - 1) - w) * (h - 1);
        if (c >= 0) {
            c = sqrt(c);
            res += integ(1, h) - integ(c, h) + c * w;
        } else {
            res += integ(1, h);
        }
        swap(w, h);
    }
    return res;
}

int main() {
    ios_base::sync_with_stdio(0); cin.tie(0);
    int n;
    cin >> n;
    vector<P> nums(n);
    for (P&p:nums) cin >> p.first >> p.second;
    cout << setprecision(100);
    if (n == 4) {
        D res = 0;
        for (int i = 0; i < n; i++) {
            auto [x1, y1] = nums[i];
            auto [x2, y2] = nums[(i+1)%n];
            res += x1*y2-y1*x2;
        }
        cout << abs(res/2) << '\n';
    } else {
        for (int i = 0; i < n; i++) {
            auto [x1, y1] = nums[(i-1+n)%n];
            auto [x2, y2] = nums[i];
            auto [x3, y3] = nums[(i+1)%n];
            if ((x2-x1)*(y3-y1)-(x3-x1)*(y2-y1) < 0) {
                auto [ox, oy] = nums[(i+3)%n];
                D sx = x2 - ox, sy = y2 - oy;
                D w = (nums[(i-1+n)%n].first - ox) / sx;
                D h = (nums[(i+1)%n].second - oy) / sy;
                // cout << ox << " " << oy << " " << sx << " " << sy << " " << w << " " << h << "\n";
                cout << abs(calcSol(w, h) * sx * sy) << '\n';
                return 0;
            }
        }
    }
    
}