#include<iostream>
#include<queue>
#include<algorithm>
#include<cmath>
#define int long long
using namespace std;
typedef long double ld;
typedef long long ll;
const int MX=200020;
const int inf=1e18;

int T, N, top, cnt, t2;
int read()
{
    int r=0, f=1; char ch=getchar();
    while(ch<'0'||ch>'9') {if(ch=='-') f=-1; ch=getchar();}
    while(ch>='0'&&ch<='9') {r=r*10+ch-'0'; ch=getchar();}
    return r*f;
}
struct point
{
    ll x, y;
    bool operator == (const point &a) const {return (x==a.x&&y==a.y);}
    point operator - (const point &a) const{return {x-a.x,y-a.y};}
    ll operator ^ (const point &a) const{return x*a.y-y*a.x;}
}p[MX], stac[MX], np[MX], ns[MX];
int qua(point p)
{
    if(p.x>=0&&p.y<0) return 1;
    if(p.x>0&&p.y>=0) return 2;
    if(p.x<=0&&p.y>0) return 3;
    if(p.x<0&&p.y<=0) return 4;
    return 5;
}
bool cmp(point a, point b)
{
    if(qua(a-p[1])!=qua(b-p[1])) return qua(a-p[1])<qua(b-p[1]);
    else return ((a-p[1])^(b-p[1]))>0;
}
bool cmp2(point a, point b)
{
    if(qua(a-np[1])!=qua(b-np[1])) return qua(a-np[1])<qua(b-np[1]);
    else return ((a-np[1])^(b-np[1]))>0;
}
ld dis(point a, point b){return sqrt(1.0*(a.x-b.x)*(a.x-b.x)+1.0*(a.y-b.y)*(a.y-b.y));}
ld getd(point a, point b, point c)
{                                 
    ld d1=dis(a,b), d2=dis(b,c), d3=dis(a,c);
    ld p=(d1+d2+d3)/2;
    return sqrt(p*(p-d1)*(p-d2)*(p-d3))*2/d1;
}
int nxt(int x){return x==t2?1:x+1;}
signed main()
{
    // freopen("testdata.in","r",stdin);
    T=read();
    while(T--)
    {
        N=read();
        int id=1;
        for(int i=1;i<=N;i++)
        {
            scanf("%lld%lld",&p[i].x,&p[i].y);
            if(p[i].x<p[id].x||(p[i].x==p[id].x&&p[i].y<p[id].y)) id=i;
        }
        swap(p[1],p[id]);
        sort(p+2,p+1+N,cmp);
        top=0;
        stac[++top]=p[1];
        for(int i=2;i<=N;i++)
        {
            while(top>=2&&((stac[top]-stac[top-1])^(p[i]-stac[top]))<=0) top--;
            stac[++top]=p[i];
        }
        stac[++top]=p[1];
        ll ans=0, now=0; 
        for(int i=1;i<top;i++)
        {
            now+=(stac[i].x*stac[i+1].y-stac[i+1].x*stac[i].y);
        }
        cnt=0;
        for(int i=1,j=1;i<=N;i++) 
        {
            if(p[i]==stac[j]) j++;
            else np[++cnt]=p[i];
        }
        // cout << "top=" << top << ", cnt=" << cnt << '\n';
        if(!cnt) {cout << "-1\n"; continue;}
        id=1;
        for(int i=1;i<=cnt;i++)
            if(np[i].x<np[id].x||(np[i].x==np[id].x&&np[i].y<np[id].y)) id=i;
        swap(np[1],np[id]);
        sort(np+2,np+1+cnt,cmp2);
        t2=0;
        ns[++t2]=np[1];
        for(int i=2;i<=cnt;i++)
        {
            while(t2>=2&&((ns[t2]-ns[t2-1])^(np[i]-ns[t2]))<=0) t2--;
            ns[++t2]=np[i];
        }
        ns[++t2]=np[1];
        int tmp=inf;
        for(int i=1;i<t2;i++)
            if(getd(stac[1],stac[2],ns[i])<tmp) tmp=getd(stac[1],stac[2],ns[i]), id=i;
        for(int i=1;i<top;i++)
        {
            while(getd(stac[i],stac[i+1],ns[id])>getd(stac[i],stac[i+1],ns[nxt(id)])) 
                id=nxt(id); 
            ll d1=stac[i].x*stac[i+1].y-stac[i+1].x*stac[i].y;
            ll d2=stac[i].x*ns[id].y-ns[id].x*stac[i].y;
            ll d3=ns[id].x*stac[i+1].y-stac[i+1].x*ns[id].y;
            ans=max(ans,abs(now-d1+d2+d3));
        }
        if(ans==0) cout << "-1\n";
        else cout << ans << '\n';
    }
    return (0-0);
}