#include<cstdio>#include<cstring>#include<algorithm>#include<iostream>#include<cmath>using namespace std;#define MAXN 1510const double EPS=1e-12;struct point{ double x,y; } convex[MAXN];struct line{ point a,b; double ang; }l[MAXN],st[MAXN];int n,ccnt; double operator *(const point &x,const point &y) { return x.x*y.y-x.y*y.x; } point operator -(point x,const point &y) { x.x-=y.x,x.y-=y.y; return x; } point operator *(const line &x,const line &y) { double a1=(y.b-x.a)*(y.a-x.a),a2=(y.a-x.b)*(y.b-x.b); point r; r.x=(x.a.x*a2+x.b.x*a1)/(a2+a1); r.y=(x.a.y*a2+x.b.y*a1)/(a2+a1); return r; } bool operator ==(const point &a,const point &b) { return fabs(a.x-b.x)<EPS&&fabs(a.y-b.y)<EPS; } bool operator <(const line &x,const line &y){ if(fabs(x.ang-y.ang)<EPS) return (y.b-x.a)*(x.b-y.a)>EPS; return x.ang<y.ang;}bool judgeout(const line &x,const point &p){return (p-x.a)*(x.b-x.a)>EPS; }bool parellel(const line &x,const line &y){ return fabs((x.b-x.a)*(y.b-y.a))<-EPS; }void inputdata(){ scanf("%d",&n); scanf("%lf%lf",&l[0].b.x,&l[0].b.y); l[n-1].a.x=l[0].b.x,l[n-1].a.y=l[0].b.y; for(int i=1;i<n;i++) { scanf("%lf%lf",&l[i].b.x,&l[i].b.y); l[i-1].a.x=l[i].b.x,l[i-1].a.y=l[i].b.y; } for(int i=0;i<n;i++) l[i].ang=atan2(l[i].b.y-l[i].a.y,l[i].b.x-l[i].a.x);}double hplaneintersection(){ int top=1,bot=0; sort(l,l+n); int tmp=1; for(int i=1;i<n;++i) if(l[i].ang-l[i-1].ang>EPS) l[tmp++]=l[i]; n=tmp; st[0]=l[0],st[1]=l[1]; for(int i=2;i<n;++i) { if(parellel(st[top],st[top-1])||parellel(st[bot],st[bot+1])) return 0; while(bot<top&&judgeout(l[i],st[top]*st[top-1])) top--; while(bot<top&&judgeout(l[i],st[bot]*st[bot+1])) bot++; st[++top]=l[i]; } while((bot<top&&judgeout(st[bot],st[top]*st[top-1]))) top--; while((bot<top&&judgeout(st[top],st[bot]*st[bot+1])))bot++; if(top<bot+1) return 0.00; st[++top]=st[bot]; ccnt=0; for(int i=bot;i<top;i++) convex[ccnt++]=st[i]*st[i+1]; double ans=0; convex[ccnt]=convex[0]; for(int i=0;i<ccnt;i++) ans+=convex[i]*convex[i+1]; return ans/2;}double chackdirection(){ double ans=0; for(int i=0;i<n;++i) ans+=l[i].a*l[i].b; return ans;}void changedirection(){ for(int i=0;i<n;++i) swap(l[i].a,l[i].b);}int main(){ int t; scanf("%d",&t); while(t--) { inputdata(); if(chackdirection()<0) changedirection(); printf("%.2fn",hplaneintersection()); } return 0;}
