#include <bits/stdc++.h>
using namespace std ;
int sgn(long long x)
{
    if(x < 0)  return -1 ;
    if(x > 0)  return 1 ;
    return 0 ;
}
struct point {
    int x, y;
    point() {}
    point(int x2, int y2) { x = x2, y = y2; }
    void input() {
        int x2, y2;
        cin >> x2 >> y2;
        x = x2;
        y = y2;
    }
    point operator+(const point &s) const { return (point){x + s.x, y + s.y}; }
    point operator-(const point &s) const { return (point){x - s.x, y - s.y}; }
    bool operator<(point b) const { return x - b.x == 0 ? y - b.y < 0 : x < b.x; }
};
using vec = point ;
long long cross(vec s, vec t) { return 1ll * s.x * t.y - 1ll * s.y * t.x; }
void Convex_Hull(vector<point> P, vector<point> &res, int flag = 1) {
    int n = P.size();
    res.resize(0);
    res.resize(n * 2);
    sort(P.begin(), P.end());
    int now = -1;
    for (int i = 0; i < (int)P.size(); i++) {
        while (now > 0 && sgn(cross(res[now] - res[now - 1], P[i] - res[now - 1])) < flag) now--;
        res[++now] = P[i];
    }
    int pre = now;
    for (int i = n - 2; i >= 0; i--) {
        while (now > pre && sgn(cross(res[now] - res[now - 1], P[i] - res[now - 1])) < flag) now--;
        res[++now] = P[i];
    }
    res.resize(now);
}
void solve()
{
    int n ;
    cin >> n ;
    vector<point> p(n) ;
    for(int i = 0 ; i < n ; i ++)  p[i].input() ;
    vector<point> A ;
    Convex_Hull(p , A) ;
    set<point> s ;
    for(int i = 0 ; i < n ; i ++)  s.insert(p[i]) ;
    for(auto u : A)  s.erase(u) ;
    vector<point> p2 ;
    for(auto u : s)  p2.push_back(u) ;
    if(p2.empty())
    {
        cout << -1 << '\n' ;
        return ;
    }
    long long ans = 0 ;
    vector<point> pp = A ;
    for (int i = 0; i < (int)pp.size(); i++) ans += cross(pp[i], pp[(i + 1) % (int)pp.size()]);
    ans = abs(ans) ;
    long long mn = 9e18 ;
    if(p2.size() <= 3)
    {
        int m = A.size() ;
        for(int i = 0 ; i < m ; i ++)
        {
            point u = A[i] ;
            point v = A[(i + 1) % m] ;
            for(auto w : p2)  mn = min(mn , abs(cross(v - u , w - u))) ;
        }
    }
    else
    {
        vector<point> B ;
        Convex_Hull(p2 , B) ;
        int m = A.size() ;
        int m2 = B.size() ;
        for(int i = 0 , j = 0 ; i < m ; i ++)
        {
            point u = A[i] ;
            point v = A[(i + 1) % m] ;
            while(true)
            {
                point w = B[j] ;
                point w2 = B[(j + 1) % m2] ;
                long long z = abs(cross(w - u , v - u)) ;
                long long z2 = abs(cross(w2 - u , v - u)) ;
                mn = min({mn , z , z2}) ;
                if(z2 <= z)  j += 1 ;
                else  break ;
            }
        }
    }

    cout << ans - mn << '\n' ;
}
int main()
{
    std::ios::sync_with_stdio(false) , cin.tie(0) ;

    int T ;
    cin >> T ;
    while (T --)  solve() ;
    return 0 ;
}