#include<bits/stdc++.h>
#define double long long
#define int long long
using namespace std;
constexpr int inf=8e18;
template <typename T>
inline void read(T& x)
{
    T f = 1;
    x = 0;
    char ch = getchar();
    while (0 == isdigit(ch))
    {
        if (ch == '-')
            f = -1;
        ch = getchar();
    }
    while (0 != isdigit(ch))
        x = (x << 1) + (x << 3) + ch - '0', ch = getchar();
    x *= f;
}

template <typename T>
inline void write(T x)
{
    if (x < 0)
    {
        x = ~(x - 1);
        putchar('-');
    }
    if (x > 9)
        write(x / 10);
    putchar(x % 10 + '0');
}
int absuse(int lop)
{
    if(lop<0)
        lop = -lop;
    return lop;
}
class Point
{
public:
    int x, y;
    Point(double x = 0, double y = 0) :x(x), y(y) {}
    Point operator + (Point a)
    {
        return Point(x + a.x, y + a.y);
    }
    Point operator - (Point a)
    {
        return Point(x - a.x, y - a.y);
    }
    bool operator < (const Point& a) const
    {
        if (x == a.x) return y < a.y;
        return x < a.x;
    }
};

typedef vector<Point> Polygom;
typedef Point Vector;

int cross(Vector a, Vector b)
{
    return a.x * b.y - a.y * b.x;
}

bool isclock(Point p0, Point p1, Point p2)
{
    Vector a = p1 - p0;
    Vector b = p2 - p0;
    if (cross(a, b) < 0) return true;
    return false;
}

int getArea(Polygom a)
{
    int ans = 0;
    for (int i = 1; i < a.size() - 1; i++)
    {
        Vector x1 = a[i] - a[0];
        Vector x2 = a[i + 1] - a[0];
        ans += absuse(cross(x1, x2));
    }
    return ans;
}

Polygom andrewScan(Polygom s)
{
    Polygom u, l;
    if (s.size() < 3) return s;
    sort(s.begin(), s.end());
    u.push_back(s[0]);
    u.push_back(s[1]);
    l.push_back(s[s.size() - 1]);
    l.push_back(s[s.size() - 2]);

    for (int i = 2; i < s.size(); i++)
    {
        for (int n = u.size(); n >= 2 && isclock(u[n - 2], u[n - 1], s[i]) != true; n--)
            u.pop_back();
        u.push_back(s[i]);
    }

    for (int i = s.size() - 3; i >= 0; i--)
    {
        for (int n = l.size(); n >= 2 && isclock(l[n - 2], l[n - 1], s[i]) != true; n--)
            l.pop_back();
        l.push_back(s[i]);
    }

    for (int i = 1; i < l.size() - 1; i++) u.push_back(l[i]);
    return u;
}
int Area2(Point A, Point B, Point C)
{
    return absuse(A.x * B.y + B.x * C.y + C.x * A.y - A.x * C.y - B.x * A.y - C.x * B.y);
}
void solve(void)
{
    int n;
    Polygom a;
    Polygom op;
    read(n);
    for (int i = 1; i <= n; i++)
    {
        Point q;
        read(q.x);
        read(q.y);
        a.push_back(q);
        op.push_back(q);
    }
    a = andrewScan(a);
    if (a.size() == n)
    {
        cout << "-1" << endl;
    }
    else
    {
        int nowsum = getArea(a);
        map<pair<int, int>, int>mp;
        for (int i = 0; i < a.size(); i++)
        {
            mp[{a[i].x, a[i].y}] = 1;
        }
        a.push_back(a[0]);
        Polygom pp;
        for (int j = 0; j < op.size(); j++)
        {
            if (mp[{op[j].x, op[j].y}] == 0)pp.push_back(op[j]);
        }
        if (pp.size()<3)
        {
            int Min = inf;
            // write(Min);

            for (int i = 0; i < a.size() - 1; i++)
            {
                for (int j = 0; j < pp.size(); j++)
                {
                    Min = min(Area2(a[i], a[i + 1], pp[j]), Min);
                }
            }
            write(nowsum - Min);
            cout << endl;
        }
        else
        {
            pp = andrewScan(pp);
            int now = 0;
            int Min = inf;
            for (int i = 0; i < pp.size(); i++)
            {
                int ppl = Area2(pp[i], a[1], a[0]);
                if (ppl < Min)
                {
                    now = i;
                    Min = ppl;
                }
            }
            int Minall = inf;
            for (int i = 0; i < a.size() - 1; i++)
            {
                int cop = now%pp.size();
                int fonow = Area2(a[i], a[i + 1], pp[now]);
                while (Area2(a[i], a[i + 1], pp[(now + 1) % pp.size()]) <= fonow)
                {
                    if ((now + 1) % pp.size() == cop)break;
                    fonow = Area2(a[i], a[i + 1], pp[(now + 1) % pp.size()]);
                    now=(now+1)%pp.size();
                }
                Minall = min(fonow, Minall);
            }
            //cout << summax << endl;
            write(nowsum - Minall);
            cout << endl;
        }
    }
}
signed main(void)
{
    

    signed t;
    cin >> t;
    while (t--)
        solve();
    return 0;
}