#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <cmath>
#include <queue>
#include <set>
#include <map>
#include <bitset>
#include <random>
#include <ctime>
#include <chrono>
#include <numeric>
#include <iomanip>
#include <cassert>

typedef long long ll;
typedef double lf;

// #define DEBUG 1
struct IO
{
    #define MAXSIZE (1 << 20)
    #define isdigit(x) (x >= '0' && x <= '9')
    char buf[MAXSIZE], *p1, *p2;
    char pbuf[MAXSIZE], *pp;
    #if DEBUG
    #else
    IO() : p1(buf), p2(buf), pp(pbuf) {}
    ~IO() {fwrite(pbuf, 1, pp - pbuf, stdout);}
    #endif
    #define gc() (p1 == p2 && (p2 = (p1 = buf) + fread(buf, 1, MAXSIZE, stdin), p1 == p2) ? ' ' : *p1++)
    #define blank(x) (x == ' ' || x == '\n' || x == '\r' || x == '\t')

    template <typename T>
    void Read(T &x)
    {
        #if DEBUG
        std::cin >> x;
        #else
        bool sign = 0; char ch = gc(); x = 0;
        for (; !isdigit(ch); ch = gc())
            if (ch == '-') sign = 1;
        for (; isdigit(ch); ch = gc()) x = x * 10 + (ch ^ 48);
        if (sign) x = -x;
        #endif
    }
    void Read(char *s)
    {
        #if DEBUG
        std::cin >> s;
        #else
        char ch = gc();
        for (; blank(ch); ch = gc());
        for (; !blank(ch); ch = gc()) *s++ = ch;
        *s = 0;
        #endif
    }
    void Read(char &c) {for (c = gc(); blank(c); c = gc());}

    void Push(const char &c)
    {
        #if DEBUG
        putchar(c);
        #else
        if (pp - pbuf == MAXSIZE) fwrite(pbuf, 1, MAXSIZE, stdout), pp = pbuf;
        *pp++ = c;
        #endif
    }
    template <typename T>
    void Write(T x)
    {
        if (x < 0) x = -x, Push('-');
        static T sta[35];
        int top = 0;
        do sta[top++] = x % 10, x /= 10; while (x);
        while (top) Push(sta[--top] ^ 48);
    }
    template <typename T>
    void Write(T x, char lst) {Write(x), Push(lst);}
} IO;
#define Read(x) IO.Read(x)
#define Write(x, y) IO.Write(x, y)
#define Put(x) IO.Push(x)

using namespace std;

const int MAXN = 1e5 + 10;

int n;

struct point
{
    ll x, y;
    point(ll _x = 0, ll _y = 0) : x(_x), y(_y) {}
    bool operator < (const point &u) const { return x == u.x ? y < u.y : x < u.x; }
    point operator - (const point &u) const { return point(x - u.x, y - u.y); }
};
inline ll det(const point &u, const point &v) { return u.x * v.y - u.y * v.x; }
inline bool turn_left(const point &u, const point &v, const point &w) { return det(v - u, w - u) > 0; }

vector <point> a, b, tmp;
map <point, bool> vis;

inline vector <point> convex_hull(vector <point> &f)
{
    sort(f.begin(), f.end());
    if (f.size() <= 2) return f;
    vector <point> g, h;
    for (auto x : f)
    {
        while (g.size() > 1 && !turn_left(g[g.size() - 2], g[g.size() - 1], x)) g.pop_back();
        g.push_back(x);
    }
    reverse(f.begin(), f.end());
    for (auto x : f)
    {
        while (h.size() > 1 && !turn_left(h[h.size() - 2], h[h.size() - 1], x)) h.pop_back();
        h.push_back(x);
    }
    for (int i = 1; i < h.size() - 1; i++) g.push_back(h[i]);
    return g;
}

int main()
{
    #if DEBUG
    #else
    ios::sync_with_stdio(0), cin.tie(0);
    #endif
    int T;
    Read(T);
    while (T--)
    {
        Read(n);
        a.clear();
        for (int i = 1, x, y; i <= n; i++) Read(x), Read(y), a.emplace_back(x, y);
        b = convex_hull(a);
        vis.clear(); for (auto x : b) vis[x] = 1;
        tmp = a, a.clear();
        for (auto x : tmp)
            if (!vis[x]) a.push_back(x);
        if (!a.size()) { cout << "-1\n"; continue; }
        a = convex_hull(a);
        ll area = 0;
        for (int i = 1; i < b.size() - 1; i++) area += det(b[i] - b[0], b[i + 1] - b[0]);
        ll ans = 0;
        b.push_back(b[0]), a.push_back(a[0]);
        for (int i = 0, j = 0; i < b.size() - 1; i++)
        {
            while (j < a.size() - 1 && !turn_left(point(0, 0), b[i + 1] - b[i], a[j + 1] - a[j])) j++;
            ans = max(ans, area - abs(det(b[i] - a[j], b[i + 1] - a[j])));
        }
        cout << ans << "\n";
    }
    return 0;
}