#include<bits/stdc++.h>
using namespace std;
typedef long long i64;

struct point {
    i64 x, y;
    point(i64 x = 0, i64 y = 0): x(x), y(y) {}
    i64 hval() {return ((x + 1000000000LL) << 31) | (y + 1000000000LL);}
};

struct arrow {
    i64 x, y;
    arrow(i64 x = 0, i64 y = 0): x(x), y(y) {}
    arrow(point a, point b): x(b.x - a.x), y(b.y - a.y) {}
};

bool operator == (const point &a, const point &b) {
    return a.x == b.x && a.y == b.y;
}
bool operator < (const point &a, const point &b) {
    if(a.x == b.x) return a.y < b.y;
    else return a.x < b.x;
}
i64 dot(const arrow &a, const arrow &b) {
    return a.x * b.x + a.y * b.y;
}
i64 cross(const arrow &a, const arrow &b) {
    return a.x * b.y - a.y * b.x;
}
// 三角形面积的两倍
i64 area(const point &a, const point &b, const point &c) {
    return abs(cross({a, b}, {a, c}));
}

// 将参数 v 变成一个凸包，逆时针排序，v[0] 是坐标最小的点
void makeConvex(vector<point> &v) {
    sort(v.begin(), v.end());
    v.erase(unique(v.begin(), v.end()), v.end());
    vector<point> t;
    for(int cnt = 0; cnt < 2; cnt++) {
        reverse(v.begin(), v.end());
        stack<point> p; stack<arrow> e;
        p.push(v[0]);
        for(int i = 1; i < v.size(); i++) {
            // 下面这个 while 会导致凸包上任意三个点都不在同一个直线上
            // 如果需要保留凸包边中间的点，把 >= 改成 > 即可
            while(!e.empty() && cross(e.top(), {p.top(), v[i]}) >= 0) 
                p.pop(), e.pop();
            e.push(arrow(p.top(), v[i]));
            p.push(v[i]);
        }
        while(p.size() > 1) 
            t.push_back(p.top()), p.pop();
    }
    v = t;
}

void solve() {
    i64 n, ans = 0, mint = 8e18; cin >> n;
    vector<point> v, t, temp;
    unordered_set<i64> mp;
    for(int i = 1; i <= n; i++) {
        i64 x, y; cin >> x >> y;
        v.push_back({x, y});
        temp.push_back({x, y});
    }
    makeConvex(v); v.push_back(v[0]);
    for(int i = 1; i < v.size(); i++) {
        ans += area(v[0], v[i], v[i - 1]);
    }
    for(auto p : v) {
        mp.insert(p.hval());
    }
    for(auto p : temp) {
        if(!mp.count(p.hval())) t.push_back(p);
    }
    if(t.size() == 0) {cout << "-1" << endl; return;}
    else if(t.size() < 3) {
        for(auto p : t) for(int i = 1; i < v.size(); i++)
            mint = min(mint, area(p, v[i], v[i - 1]));
        cout << ans - mint << endl;
    } else {
        makeConvex(t); int szt = t.size(), p = 0;
        for(int i = 0; i < szt * 2; i++) {
            t.push_back(t[i]);
        }
        for(int i = 0; i < szt; i++) {
            if(area(v[0], v[1], t[i]) < area(v[0], v[1], t[p])) p = i;
        }
        for(int i = 1; i < v.size(); i++) {
            while(area(v[i], v[i - 1], t[p + 1]) <= area(v[i], v[i - 1], t[p])) p++;
            mint = min(mint, area(v[i], v[i - 1], t[p]));
        }
        cout << ans - mint << endl;
    }
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    int T; cin >> T;
    while(T--) solve();
    return 0;
}