#include<bits/stdc++.h>
#define For(i,a,b) for(int i=(a);i<=(b);++i)
#define Rep(i,a,b) for(int i=(a);i>=(b);--i)
#define int long long
using namespace std;
inline int read()
{
    int x;cin>>x;return x;
}

#define fi first
#define se second
#define pb push_back
#define mkp make_pair
typedef pair<int,int>pii;
typedef vector<int>vi;

#define maxn 250005
#define inf 0x3f3f3f3f

typedef double db;
const db eps=1e-8,pi=3.14159265358979323846;
int sgn(db x){return x<-eps?-1:x>eps;}
int cmp(db a,db b){return sgn(a-b);}

struct P{
	int x,y,id;
	P(int x=0,int y=0):x(x),y(y){}
	P&operator +=(P o){return x+=o.x,y+=o.y,*this;}
	P&operator -=(P o){return x-=o.x,y-=o.y,*this;}
	P&operator *=(int o){return x*=o,y*=o,*this;}
	P&operator /=(int o){return x/=o,y/=o,*this;}
	friend P operator +(P a,P b){return a+=b;}
	friend P operator -(P a,P b){return a-=b;}
	friend P operator *(P a,int b){return a*=b;}
	friend P operator /(P a,int b){return a/=b;}
	friend bool operator <(P a,P b){return fabs(a.x-b.x)<eps?a.y<b.y:a.x<b.x;}
	friend bool operator ==(P a,P b){return cmp(a.x,b.x)==0 && cmp(a.y,b.y)==0;}
	friend bool operator !=(P a,P b){return !(a==b);}
	friend int operator %(P a,P b){return a.x*b.x+a.y*b.y;} // dot
	friend int operator *(P a,P b){return a.x*b.y-a.y*b.x;} // cross
	
	P rot90(){return P(-y,x);}
	db ang(){return atan2(y,x);}
	db len(){return sqrt(x*x+y*y);}
	int len2(){return x*x+y*y;}
	
	int half(){return sgn(y)==1||(sgn(y)==0&&sgn(x)>=0);}
//	P unit(){return ((*this))/len();}
	
	void read(){cin>>x>>y;}
	void out(){cout<<"("<<x<<","<<y<<")"<<endl;}
};
bool cmp_dir(P a,P b){
	if(a.half()!=b.half())return a.half()<b.half();
	return sgn(a*b)>0;
}

db dis(P a,P b){return (a-b).len();}
int cross(P a,P b,P c){
	// (a->b)*(a->c)
	return (b.x-a.x)*(c.y-a.y)-(b.y-a.y)*(c.x-a.x);
}
int cmp3(P a,P b,P c){
	return sgn(cross(a,b,c));
}

vector<P>convex(vector<P>a){
	int n=a.size(),m=0; if(n<=2)return a;
	sort(a.begin(),a.end());
	vector<P>st(n*2); int tp=0;
	For(i,0,n-1){
		while(tp>1 && cmp3(st[tp-2],st[tp-1],a[i])<=0)--tp;
		st[tp++]=a[i];
	}
	int t=tp;
	Rep(i,n-2,0){
		while(tp>t && cmp3(st[tp-2],st[tp-1],a[i])<=0)--tp;
		st[tp++]=a[i];
	}
	st.resize(tp-1);
	return st;
}

int n;
vector<P>a;
bool vis[maxn];

int area(vector<P>a){
    int res=0; int n=a.size();
    For(i,0,n-1) res+=a[i]*a[(i+1)%n];
    return res;
}
int S(P a,P b,P c){
    return abs(cross(a,b,c));
}
void work()
{
    n=read();
    For(i,0,n) vis[i]=0;
    a.resize(n);
    For(i,0,n-1){
        a[i].x=read(),a[i].y=read();
        a[i].id=i;
    }
    auto b=convex(a);
    vector<P>c;
    for(auto p:b) vis[p.id]=1;
    For(i,0,n-1) if(!vis[i]) c.pb(a[i]);
    if(!c.size()){
        puts("-1");
        return;
    }
    c=convex(c);
    int s=area(b);
    
    int mn=4e18;

    int p=0;
    For(i,0,c.size()-1) if(S(b[0],b[1],c[i]) < S(b[0],b[1],c[p])) p=i;
    mn=min(mn,S(b[0],b[1],c[p]));

    For(i,0,b.size()-1){
        int ii=(i+1)%b.size();
        while(S(b[i],b[ii],c[(p+1)%c.size()]) < S(b[i],b[ii],c[p])) p=(p+1)%c.size();
        while(S(b[i],b[ii],c[(p-1+c.size())%c.size()]) < S(b[i],b[ii],c[p])) p=(p-1+c.size())%c.size();
        mn=min(mn,S(b[i],b[ii],c[p]));
    }
    cout<<s-mn<<"\n";
}

signed main()
{
   // cout<<(4.5*sqrt(2))<<"\n";
    int T=read();
    while(T--)work();
	return 0;
}
/*

*/