#include <bits/stdc++.h>
using namespace std;
static constexpr int Maxn = 1e5 + 5;
using int_t = int64_t;
using real_t = long double;
struct point {
  int_t x, y;
  point() { }
  point(int_t x, int_t y) : x(x), y(y) { }
  friend point operator + (const point &lhs, const point &rhs) { return point(lhs.x + rhs.x, lhs.y + rhs.y); }
  friend point operator - (const point &lhs, const point &rhs) { return point(lhs.x - rhs.x, lhs.y - rhs.y); }
  friend int_t operator * (const point &lhs, const point &rhs) { return lhs.x * rhs.x + lhs.y * rhs.y; }
  int_t abs(void) const { return x * x + y * y; }
  friend bool operator < (const point &lhs, const point &rhs) { return lhs.x < rhs.x || (lhs.x == rhs.x && lhs.y < rhs.y); }
}; int_t det(const point &a, const point &b) { return a.x * b.y - a.y * b.x; }
int_t area2(const point &a, const point &b, const point &c) { return abs(det(b - a, c - a)); }
int sgn(int_t x) { return x == 0 ? 0 : (x > 0 ? 1 : -1); }
real_t distance(point p, point x, point y) { return abs((real_t)det(y - x, p - x) / (y - x).abs()); }
bool turn_left(const point &a, const point &b, const point &c)
{ return sgn(det(b - a, c - a)) >= 0; }
vector<point> convex_hull(vector<point> a) {
  int n = (int)a.size(), cnt = 0;
  if (n < 2) return a;
  sort(a.begin(), a.end(), [&](auto lhs, auto rhs)
      { return make_pair(lhs.x, lhs.y) < make_pair(rhs.x, rhs.y); });
  vector<point> ret;
  for (int i = 0; i < n; ++i) {
    while (cnt > 1 && turn_left(ret[cnt - 2], a[i], ret[cnt - 1]))
      --cnt, ret.pop_back();
    ++cnt, ret.push_back(a[i]);
  } int fixed = cnt;
  for (int i = n - 2; i >= 0; --i) {
    while (cnt > fixed && turn_left(ret[cnt - 2], a[i], ret[cnt - 1]))
      --cnt, ret.pop_back();
    ++cnt, ret.push_back(a[i]);
  } ret.pop_back(); return ret;
} // convex_hull
int_t calc_area(const vector<point> &a) {
  int_t ret = 0;
  for (int i = 1; i < (int)a.size() - 1; ++i)
    ret += area2(a[0], a[i], a[i + 1]);
  return ret;
} // calc_area
int main(void) {
  cin.tie(nullptr)->sync_with_stdio(false);
  int tests; cin >> tests;
  while (tests--) {
    int n; cin >> n; vector<point> a(n), c;
    for (auto &[x, y]: a) cin >> x >> y;
    auto b = convex_hull(a); set<point> sb;
    auto area = calc_area(b);
    for (auto z: b) sb.insert(z);
    for (auto z: a) if (sb.find(z) == sb.end()) c.push_back(z);
    if (c.empty()) { cout << "-1\n"; continue; }
    auto d = convex_hull(c); int p = 0;
    for (int i = 0; i < (int)d.size(); ++i)
      if (distance(d[i], b[0], b[1]) < distance(d[p], b[0], b[1])) p = i;
    auto tri = area2(d[p], b[0], b[1]);
    for (int i = 1, q = p; i < (int)b.size(); ++i) {
      point x = b[i], y = b[(i + 1) % (int)b.size()];
      while (distance(d[(q + 1) % (int)d.size()], x, y) <= distance(d[q], x, y)) ++q;
      tri = min(tri, area2(d[q], x, y));
    } cout << area - tri << endl;
  }
  return 0;
} // main