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

typedef long long ll;
const double EPS = 1e-9;

struct PT {
  double x, y;
  PT() {}
  PT(double x, double y) : x(x), y(y) {}
  PT(const PT &p) : x(p.x), y(p.y)    {}
  PT operator + (const PT &p)  const { return PT(x+p.x, y+p.y); }
  PT operator - (const PT &p)  const { return PT(x-p.x, y-p.y); }
  PT operator * (double c)     const { return PT(x*c,   y*c  ); }
  PT operator / (double c)     const { return PT(x/c,   y/c  ); }
};

double dot(PT p, PT q)     { return p.x*q.x+p.y*q.y; }
double dist2(PT p, PT q)   { return dot(p-q,p-q); }
double cross(PT p, PT q)   { return p.x*q.y-p.y*q.x; }

PT ComputeLineIntersection(PT a, PT b, PT c, PT d) {
  b=b-a; d=c-d; c=c-a;
  assert(dot(b, b) > EPS && dot(d, d) > EPS);
  return a + b*cross(c, d)/cross(b, d);
}

const int N = 101010;
int n;
PT a[N];

double area(vector<PT>pol){
double sum=0.0;
for(int i=0;i<pol.size();i++)
    sum += cross( pol[i] , pol[ (i+1)%pol.size() ] );
return fabs(sum)/2.0;
}

void solve(){

double mxY=-1;

scanf("%d",&n);
for(int i=1;i<=n;i++){
        int _xx,_yy;
        scanf("%d %d",&_xx,&_yy);
        a[i]=PT(_xx,_yy);
        mxY=max(mxY,a[i].y);
    }
int idx1,idx2;
for(int i=1;i<=n;i++)
    if( a[i].y == mxY ){
        idx1=i;
        break;
    }

for(int i=n;i>0;i--)
    if( a[i].y==mxY ){
        idx2=i;
        break;
    }

double ans=0.0;

int j=1;
for(int i=2;i<=idx1;i++){

    if( a[j].y <= a[i].y ){

        if( j+1<i ){
          vector<PT>pol;
          for(int k=j;k<i;k++)pol.push_back( a[k] );
          pol.push_back( ComputeLineIntersection(a[j],PT(1e9,a[j].y),a[i-1],a[i]) );
          ans += area(pol);
        }
        j=i;
    }
}

j=n;
for(int i=n-1;i>=idx2;i--){

    if( a[j].y <= a[i].y ){

        if( j>i+1 ){
          vector<PT>pol;
          for(int k=j;k>i;k--)pol.push_back( a[k] );
          pol.push_back( ComputeLineIntersection(a[j],PT(-1e9,a[j].y),a[i],a[i+1]) );
          ans += area(pol);
        }
        j=i;
    }
}

j=idx1;
for(int i=idx1+1;i<=idx2;i++)
if( a[i].y == mxY ){

    if( j+1<i ){
          vector<PT>pol;
          for(int k=j;k<=i;k++)pol.push_back( a[k] );
          ans += area(pol);
    }
    j=i;
}
printf("%.8f\n",ans);
}

int main(){

int t;
cin>>t;
while( t-- )solve();

return 0;
}