#include<bits/stdc++.h>
#define int long long
using namespace std;

int read() {
	char ch=getchar();
	int f=1,x=0;
	while(ch<'0'||ch>'9') {
		if(ch=='-')
			f=-1;
		ch=getchar();
	}
	while(ch>='0'&&ch<='9') {
		x=x*10+ch-'0';
		ch=getchar();
	}
	return f*x;
}
char read_char() {
	char ch=getchar();
	while(!isalpha(ch)) {
		ch=getchar();
	}
	return ch;
}

const int MAXN=2e5+10;

int n,xmn,ymn;
struct point {
	int x,y;
	bool vis;
	point operator -(const point &p) {
		return (point){x-p.x,y-p.y,0};
	}
}p[MAXN];

int cross(point a,point b) {
	return a.x*b.y-a.y*b.x;
}
bool cmp(point a,point b) {
	if(a.vis^b.vis) {
		return !a.vis;
	}
	//long double k1=(long double)(a.y-ymn)/(long double)(a.x-xmn+1e-6);
	long double k1=atan2(a.y-ymn,a.x-xmn);
	//long double k2=(long double)(b.y-ymn)/(long double)(b.x-xmn+1e-6);
	long double k2=atan2(b.y-ymn,b.x-xmn);
	int dis1=(a.y-ymn)*(a.y-ymn)+(a.x-xmn)*(a.x-xmn);
	int dis2=(b.y-ymn)*(b.y-ymn)+(b.x-xmn)*(b.x-xmn);
	if(k1!=k2) {
		return k1<k2;
	}
	return dis1<dis2;
}

vector<point> cv[2];
stack<int> s;

void find_convex(int t) {
	int idx=0;
	for(int i=1;i<=n;i++) {
		if(p[i].vis) {
			continue;
		}
		if(!idx) {
			idx=i;
		}
		if(p[i].y<p[idx].y) {
			idx=i;
		}
		else if(p[i].y==p[idx].y&&p[i].x<p[idx].x) {
			idx=i;
		}
	}
	swap(p[1],p[idx]);
	ymn=p[1].y;
	xmn=p[1].x;
	sort(p+2,p+n+1,cmp);
	s.push(1);
	for(int i=2;i<=n;i++) {
		if(p[i].vis) {
			break;
		}
		while(s.size()>1) {
			int tp=s.top();
			s.pop();
			if(cross(p[tp]-p[s.top()],p[i]-p[tp])<0) {
				;
			}
			else {
				s.push(tp);
				break;
			}
		}
		s.push(i);
	}
	
	while(!s.empty()) {
		cv[t].push_back(p[s.top()]);
		p[s.top()].vis=1;
		s.pop();
	}
}

void solve() {
	cin>>n;
	for(int i=1;i<=n;i++) {
		p[i].x=read();p[i].y=read();
		p[i].vis=0;
	}
	
	find_convex(0);
	find_convex(1);
	if(cv[0].size()==n) {
		puts("-1");
		return ;
	} 
	
	for(int t=0;t<2;t++) {
		int sz=cv[t].size();
		for(int i=0;i<sz;i++) {
			cv[t].push_back(cv[t][i]);
		}
	}
	for(int t=0;t<2;t++) {
		int sz=cv[t].size();
		for(int i=0;i<sz;i++) {
			cv[t].push_back(cv[t][i]);
		}
	}
	
	int pos=0,mn=5e18,sum=0;
	int sz=cv[0].size();
	for(int j=0;j<cv[1].size()/4;j++) {
		if(abs(cross(cv[0][1]-cv[0][0],cv[0][0]-cv[1][pos]))<abs(cross(cv[0][1]-cv[0][0],cv[0][0]-cv[1][j]))) {
			pos=j;
		}
	}
	for(int i=0;i<sz/4;i++) {
		while(abs(cross(cv[0][i+1]-cv[0][i],cv[0][i]-cv[1][pos]))>abs(cross(cv[0][i+1]-cv[0][i],cv[0][i]-cv[1][pos+1]))) {
			pos=(pos+1)%(cv[1].size()/4);
		}
		mn=min(mn,abs(cross(cv[0][i+1]-cv[0][i],cv[0][i]-cv[1][pos])));
		/*for(int j=0;j<cv[1].size()/4;j++) {
			mn=min(mn,abs(cross(cv[0][i+1]-cv[0][i],cv[0][i]-cv[1][j])));
		}*/
		sum+=cross(cv[0][i],cv[0][i+1]);
	}
	sum=abs(sum); 
	cout<<(sum-mn)<<endl;
}

signed main() {
	//freopen(".in","r",stdin);
	//freopen(".out","w",stdout);
	
	int t=read();
	while(t--) {
		solve();
		cv[1].clear();
		cv[0].clear();
	}

	//fclose(stdin);
	//fclose(stdout);
	return 0;
}