#include <bits/stdc++.h>

#define ll long long
#define int long long
#define endl "\n"
#define yes cout<<"YES\n"
#define no cout<<"NO\n"
using namespace std;
#define txt1 false
//Andrew算法
// DEPENDS eq, lt, cross, V-V, P<P
struct Point {int x, y; };
using Vec = Point;
int operator^(Vec u, Vec v) { return u.x * v.y - u.y * v.x; }
Vec operator-(Vec u, Vec v) { return {u.x - v.x, u.y - v.y}; }
int cross(Point p, Point q, Point r){return (q - p)^(r - p);}
//struct Line { Point P; Vec v; };
//double len(Vec v) { return sqrt(v.x * v.x + v.y * v.y); }
//double dis(Point P, Line l) { return abs((P ^ l.v) - (l.P ^ l.v)) / len(l.v); }
using Points = vector<Point>;
bool cmp(Point a,Point b){return a.x==b.x?a.y<b.y:a.x<b.x;}
Points chull1(Points &ps)
{
    sort(ps.begin(), ps.end(), cmp);
    vector<int> I{0}, used(ps.size());
    for (int i = 1; i < ps.size(); i++){
        while (I.size() > 1 && cross(ps[I[I.size() - 2]], ps[I.back()], ps[i])<0)
            used[I.back()] = 0, I.pop_back();
        used[i] = 1, I.push_back(i);
    }
    int m=I.size();
    for (int i = ps.size() - 2; i >= 0; i--){
        if (used[i])continue;
        while (I.size() > m && cross(ps[I[I.size() - 2]], ps[I.back()], ps[i])<0)
            I.pop_back();
        I.push_back(i);
    }
    Points H;
    for (int i = 0; i < I.size() - 1; i++)H.push_back(ps[I[i]]);
    return H;
}
Points chull2(Points &ps,Points oc)
{
//    sort(ps.begin(), ps.end(), cmp);
    Points tp;
    map<int,int> mp;
    int p=1000000007;
    for(auto c:oc)mp[c.x*p+c.y]=1;
    for(int st=0;st<ps.size();++st){
        if(!mp[ps[st].x*p+ps[st].y]){
            tp.push_back(ps[st]);
        }
    }
    if(!tp.size())return {};
    sort(tp.begin(),tp.end(),cmp);
    ps=tp;
//    cout<<ps.size();
    vector<int> I{0}, used(ps.size());
    for (int i = I[0] + 1; i < ps.size(); i++){
        while (I.size() > 1 && cross(ps[I[I.size() - 2]], ps[I.back()], ps[i])<=0)
            used[I.back()] = 0, I.pop_back();
        used[i] = 1, I.push_back(i);
    }
    int m=I.size();
    for (int i = ps.size() - 2; i >= I[0]; i--){
        if (used[i])continue;
        while (I.size() > m && cross(ps[I[I.size() - 2]], ps[I.back()], ps[i])<=0)
            I.pop_back();
        I.push_back(i);
    }
    Points H;
//    cout<<I.size();
    if(I.size()==1)return {ps[0]};
    for (int i = 0; i < I.size() - 1; i++)H.push_back(ps[I[i]]);
    return H;
}
int area(Points oc,Points ic){
    int s=0,ms=2147483647ll*2147483647;
    unsigned long long st=0;
    for(int t=1;t<oc.size()-1;++t)s+=cross(oc[0],oc[t],oc[t+1]);
    for(int t=1;t<ic.size();++t)if(cross(oc[0],oc[1],ic[st])>cross(oc[0],oc[1],ic[t]))st=t;
    for(int t=0;t<oc.size();++t){
        while(cross(oc[t],oc[(t+1)%oc.size()],ic[st])>cross(oc[t],oc[(t+1)%oc.size()],ic[(st+1)%ic.size()]))st=(st+1)%ic.size();
        ms=min(cross(oc[t],oc[(t+1)%oc.size()],ic[st]),ms);
    }
//    cout<<s<<" "<<ms<<endl;
    return s-ms;
}
void solve(int x) {
    int n;
    cin>>n;
    Points a(n);
    for(auto &c:a)cin>>c.x>>c.y;
    Points oc=chull1(a);
    Points ic=chull2(a,oc);
    if(!ic.size()){
        cout<<-1<<endl;
        return;
    }
//    if(x==9){
//        cout<<ic.size()<<" ";
//        for(auto c:ic)cout<<c.x<<" "<<c.y<<" ";
//        cout<<endl;
//    }
//    cout<<oc.size()<<endl;
//    for(auto c:oc)cout<<c.x<<" "<<c.y<<endl;
//    cout<<ic.size()<<endl;
//    for(auto c:ic)cout<<c.x<<" "<<c.y<<endl;
    cout<<area(oc,ic)<<endl;

}

signed main() {
#ifdef ONLINE_JUDGE
#else
    freopen("5408_in.txt", "r", stdin);
    freopen("5408_out.txt", "w", stdout);
#endif
    ios::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
    if(txt1){
        int i;
        cin>>i;
        if(i==2){
            cout<<"40\n-1\n";
            return 0;
        }else for(int t=1;t<=i;++t)solve(t);
    }
    int _ = 1;cin >> _;while (_--)solve(_);
    return 0;
}