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

typedef double T;
const T EPS = 1e-8;
struct Point {
    T x, y;
    Point() {}
    Point(T x, T y) : x(x), y(y) {}
    bool operator<(const Point &p) const { return tie(x, y) < tie(p.x, p.y); }
    bool operator==(const Point &p) const { return abs(x - p.x) <= EPS && abs(y - p.y) <= EPS; }
};
Point operator-(const Point &p) { return Point(-p.x, -p.y); }
Point operator-(const Point &a, const Point &b) { return Point(a.x - b.x, a.y - b.y); }
T cross(const Point &a, const Point &b) { return a.x * b.y - a.y * b.x; }
T dot(const Point &a, const Point &b) { return a.x * b.x + a.y * b.y; }
T sqlen(const Point &a) { return dot(a, a); }

vector<Point> convexHull(vector<Point> pts) {
    sort(pts.begin(), pts.end());
    pts.erase(unique(pts.begin(), pts.end()), pts.end());
    if (pts.size() <= 1) return pts;
    vector<Point> h;
    for (int phase = 0; phase < 2; ++phase) {
        auto start = h.size();
        for (auto &p : pts) {
            while (h.size() >= start + 2 && cross(h.back() - h[h.size() - 2], p - h[h.size() - 2]) <= EPS)
                h.pop_back();
            h.push_back(p);
        }
        h.pop_back();
        reverse(pts.begin(), pts.end());
    }
    return h;
}

bool onSegment(const Point &a, const Point &b, const Point &p) {
    if (abs(cross(b - a, p - a)) > EPS) return false;
    T d = dot(b - a, p - a);
    return d > -EPS && d < sqlen(b - a) + EPS;
}

bool isOnBoundary(const vector<Point> &hull, const Point &p) {
    int n = hull.size();
    for (int i = 0; i < n; ++i) {
        Point a = hull[i], b = hull[(i + 1) % n];
        if (onSegment(a, b, p)) return true;
    }
    for (const Point &q : hull)
        if (abs(p.x - q.x) <= EPS && abs(p.y - q.y) <= EPS)
            return true;
    return false;
}

string formatNumber(double value) {
    stringstream ss;
    ss << fixed << setprecision(10) << value;
    string s = ss.str();
    size_t dot_pos = s.find('.');
    if (dot_pos != string::npos) {
        size_t last_non_zero = s.find_last_not_of('0', s.size() - 1);
        if (last_non_zero == string::npos) {
            s = s.substr(0, dot_pos + 2);
        } else if (last_non_zero == dot_pos) {
            s = s.substr(0, dot_pos + 2);
        } else {
            s = s.substr(0, last_non_zero + 1);
            if (s.back() == '.') {
                s += "0";
            }
        }
    }
    return s;
}

int main() {
    int n;
    cin >> n;
    vector<Point> pts(n);
    for (int i = 0; i < n; ++i) {
        cin >> pts[i].x >> pts[i].y;
    }

    double min_area = -1;
    set<pair<double, double>> tried_centers;

    // Check all midpoints of pairs of distinct vertices
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n; ++j) {
            if (i == j) continue;
            Point p = pts[i], q = pts[j];
            double cx = (p.x + q.x) / 2.0;
            double cy = (p.y + q.y) / 2.0;
            if (tried_centers.count({cx, cy})) continue;
            tried_centers.insert({cx, cy});

            vector<Point> all = pts;
            for (const Point &pt : pts) {
                Point sym(2 * cx - pt.x, 2 * cy - pt.y);
                all.push_back(sym);
            }

            vector<Point> hull = convexHull(all);
            bool valid = true;
            for (const Point &pt : pts) {
                if (!isOnBoundary(hull, pt)) {
                    valid = false;
                    break;
                }
            }
            if (valid) {
                double area = 0;
                int m = hull.size();
                for (int k = 0; k < m; ++k) {
                    int l = (k + 1) % m;
                    area += (hull[k].x * hull[l].y - hull[k].y * hull[l].x);
                }
                area = abs(area) / 2.0;
                if (min_area < 0 || area < min_area) {
                    min_area = area;
                }
            }
        }
    }

    // For odd n, check each vertex as a possible center
    if (n % 2 == 1) {
        for (int i = 0; i < n; ++i) {
            Point c = pts[i];
            double cx = c.x;
            double cy = c.y;
            if (tried_centers.count({cx, cy})) continue;
            tried_centers.insert({cx, cy});

            vector<Point> all = pts;
            for (const Point &pt : pts) {
                Point sym(2 * cx - pt.x, 2 * cy - pt.y);
                all.push_back(sym);
            }

            vector<Point> hull = convexHull(all);
            bool valid = true;
            for (const Point &pt : pts) {
                if (!isOnBoundary(hull, pt)) {
                    valid = false;
                    break;
                }
            }
            if (valid) {
                double area = 0;
                int m = hull.size();
                for (int k = 0; k < m; ++k) {
                    int l = (k + 1) % m;
                    area += (hull[k].x * hull[l].y - hull[k].y * hull[l].x);
                }
                area = abs(area) / 2.0;
                if (min_area < 0 || area < min_area) {
                    min_area = area;
                }
            }
        }
    }

    if (min_area >= 0) {
        cout << formatNumber(min_area) << endl;
    } else {
        cout << -1 << endl;
    }
    return 0;
}