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

#define ll long long
#define int long long
struct Point
{

    ll x, y;
    double angle;

    bool operator<(Point p)
    {
        return x < p.x || (x == p.x && y < p.y);
    }
};

ll cross_product(Point O, Point A, Point B)
{
    return (A.x - O.x) * (B.y - O.y) - (A.y - O.y) * (B.x - O.x);
}

Point find_center(const std::vector<Point> &points)
{
    double center_x = 0, center_y = 0;
    for (const auto &point : points)
    {
        center_x += point.x;
        center_y += point.y;
    }
    center_x /= points.size();
    center_y /= points.size();
    return {center_x, center_y, 0};
} 

double calculate_angle(const Point& point, const Point& center) { return atan2(point.y - center.y, point.x - center.x); }

vector<pair<Point, int>> convex_hull(vector<Point>& A)
{
    //for(Point P : A) cout << P.x << " " << P.y << endl;
    int n = A.size(), k = 0;

    if (n <= 3)
    {
        vector<pair<Point, int>> res;
        for (int i = 0; i < n; ++i)
            res.push_back({A[i], i});
    }

    vector<pair<Point, int>> ans(2 * n);

    //sort(A.begin(), A.end());

    for (int i = 0; i < n; ++i)
    {
        while (k >= 2 && cross_product(ans[k - 2].first, ans[k - 1].first, A[i]) <= 0)
            k--;
        ans[k++] = {A[i], i};
    }

    for (size_t i = n - 1, t = k + 1; i > 0; --i)
    {
        while (k >= t && cross_product(ans[k - 2].first, ans[k - 1].first, A[i - 1]) <= 0)
            k--;
        ans[k++] = {A[i - 1], i - 1};
    }

    ans.resize(k - 1);

    return ans;
}

ll polygonArea(const vector<pair<Point, int>> &points)
{
    int n = points.size();
    ll area = 0;
    for (int i = 0; i < n; i++)
    {
        int j = (i + 1) % n;
        area += points[i].first.x * points[j].first.y;
        area -= points[j].first.x * points[i].first.y;
    }
    return area;
}
ll polygonArea(const vector<Point> &points)
{
    int n = points.size();
    ll area = 0;
    for (int i = 0; i < n; i++)
    {
        int j = (i + 1) % n;
        area += points[i].x * points[j].y;
        area -= points[j].x * points[i].y;
    }
    return area;
}

void solve()
{
    int n;
    cin >> n;
    vector<Point> p(n);
    for (int i = 0; i < n; ++i)
        cin >> p[i].x >> p[i].y;
    Point center = find_center(p); 
     for (auto& point : p) { point.angle = calculate_angle(point, center); }
     sort(p.begin(), p.end(), [](const Point& a, const Point& b) { return a.angle - b.angle < 1e-15;});

    //for(Point P : p) cout << P.x << " " << P.y << endl;

    vector<pair<Point, int>> hull = convex_hull(p);
    int m = hull.size();
    

    if (m == n)
    {
        cout << -1 << endl;
        return;
    }

    ll mx = LLONG_MAX;
    for(int i = 0; i < m; ++i){
        int nxt = (i + 1) % m;
        ll cur = LLONG_MAX;
        for(int j = hull[i].second + 1; j < hull[nxt].second; ++j){
            //cout << p[j].x << " " << p[j].y << endl;
            cur = min(cur, polygonArea({hull[nxt].first, p[j], hull[i].first}));
        }
        mx = min(mx, cur);
    }

    //cout << mx << endl;
    cout << polygonArea(hull) - mx << endl;
}

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

    int t;
    cin >> t;
    while(t--) solve();
}