#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
const ld eps = 1e-9;
const int N = 200010;
int n;

struct P {
	ld x, y;
	P(ld X = 0, ld Y = 0) : x(X), y(Y) {}
	inline P operator+(const P &yy)const {
		return P(x + yy.x, y + yy.y);
	}
	inline P operator-(const P &yy)const {
		return P(x - yy.x, y - yy.y);
	}
	inline ld operator*(const P &yy)const {
		return x * yy.y - y * yy.x;	
	}
	inline ld operator&(const P &yy)const {
		return x * yy.x + y * yy.y;
	}
	inline ld len() {
		return sqrtl(x * x + y * y);
	}
}; P a[N];

struct S {
	P s, t;
	S(P S = P(), P T = P()) : s(S), t(T) {}
};

int id[N], len;
vector<int> con1, con2;
bool used[N];

ld dis(S vec, P y) {
	return fabsl((vec.t - vec.s) * (y - vec.s)) / (vec.t - vec.s).len();
}
void find_con(vector<int> &con) {
	con.clear();
	len = 0;
	for(int i = 1; i <= n; i++) {
		if(used[i]) continue;
		id[++len] = i;
	}
	sort(id + 1, id + len + 1, [](int x, int y) {
		return fabsl(a[x].x - a[y].x) < eps ? a[x].y < a[y].y : a[x].x < a[y].x;
	});
	// cout << ">>> id : ";
	// for(int i = 1; i <= len; i++) cout << id[i] << " ";
	// cout << "\n";
	if(len == 0) return ;
	if(len <= 2) {
		for(int i = 1; i <= len; i++)
			con.push_back(id[i]);
		return ;
	}
	vector<int> vec1, vec2;
	vec1.push_back(id[1]);
	for(int i = 2; i <= len; i++) {
		for(; vec1.size() > 1;) {
			int x = vec1[vec1.size() - 2], y = vec1[vec1.size() - 1], z = id[i];
			if((a[y] - a[x]) * (a[z] - a[y]) > 0) break;
			vec1.pop_back();
		}
		vec1.push_back(id[i]);
	}
	reverse(id + 1, id + len + 1);
	vec2.push_back(id[1]);
	for(int i = 2; i <= len; i++) {
		for(; vec2.size() > 1;) {
			int x = vec2[vec2.size() - 2], y = vec2[vec2.size() - 1], z = id[i];
			if((a[y] - a[x]) * (a[z] - a[y]) > 0) break;
			vec2.pop_back();
		}
		vec2.push_back(id[i]);
	}
	for(auto v : vec1) con.push_back(v);
	for(int i = 1; i < (int)vec2.size() - 1; i++) con.push_back(vec2[i]);
}
void solve() {
	cin >> n;
	for(int i = 1; i <= n; i++) {
		int x, y; cin >> x >> y;
		a[i] = P(1.0 * x, 1.0 * y);
	}
	con1.clear(), con2.clear();
	for(int i = 1; i <= n; i++) used[i] = 0;
	find_con(con1);
	for(auto v : con1) used[v] = 1;
	find_con(con2);
	// cout << ">>> "; for(auto v : con1) cout << v << " "; cout << "\n";
	// cout << ">>> "; for(auto v : con2) cout << v << " "; cout << "\n";
	if(con2.size() == 0 || con1.size() <= 2) {
		cout << "-1\n"; return ;
	}
	int pos = 0; ld cur_dis = 1e18;
	for(int i = 1; i < (int)con2.size(); i++) {
		int v = con2[i];
		S seg = S(a[con1[0]], a[con1[1]]);
		ld cur = dis(seg, a[v]);
		if(cur < cur_dis) cur_dis = cur, pos = i;
	}
	ld ans = -9e18;
	for(int i = 0; i < (int)con1.size(); i++) {
		S seg = S(a[con1[i]], a[con1[(i + 1) % (int)con1.size()]]);
		for(; (int)con2.size() > 1;) {
			int v; ld cur = dis(seg, a[con2[pos]]);
			v = (pos + 1) % (int)con2.size();
			if(dis(seg, a[con2[v]]) < cur) {
				pos = v; continue;
			}
			v = (pos - 1 + (int)con2.size()) % (int)con2.size();
			if(dis(seg, a[con2[v]]) < cur) {
				pos = v; continue;
			}
			break;
		}
		ans = max(ans, -dis(seg, a[con2[pos]]) * (seg.s - seg.t).len());
	}
	for(int i = 0; i < (int)con1.size(); i++) {
		ans += a[con1[i]] * a[con1[(i + 1) % (int)con1.size()]];
	}
	cout << (ll)(ans + 0.5) << "\n";
}
int main() {
	ios::sync_with_stdio(0); cin.tie(nullptr);
	int T; cin >> T;
	for(; T; --T) solve();
	return 0;
}