#include <iostream>
#include <complex>
#include <vector>
#include <algorithm>
#include <fstream>
#include <set>
#include <cassert>
#include <cmath>
#include <iomanip>
using namespace std;

typedef complex<double> cplx;
typedef pair<cplx,cplx> edge;
typedef vector<edge> polygon;
typedef vector<cplx> vertices;

const double epsilon=0.0001;

bool edge_cross_edge(edge es, double& s, edge et, double& t){
  cplx
    a = es.first,
    u = es.second,
    b = et.first,
    v = et.second;
  double det = imag(conj(u)*v);
  if(det==0)
    return false;
  s = - imag(conj(v) * (b-a)) / det;
  t = - imag(conj(u) * (b-a)) / det;
  return true;
}

polygon thicken(polygon p,double thickness){
  for(int i=0;i<p.size();i++)
    p[i].first+=thickness*p[i].second*cplx(0,1)/abs(p[i].second);
  for(int i=0;i<p.size();i++){
    int j=(i+1)%p.size();
    double s,t;
    assert(edge_cross_edge(p[i],s,p[j],t));
    p[j].first+=p[j].second*t;
  }
  for(int i=0;i<p.size();i++){
    int j=(i+1)%p.size();
    p[i].second=p[j].first-p[i].first;
  }
  return p;
}

ostream& operator<<(ostream& o,polygon p){
  for(int i=0;i<p.size();i++){
    if(i)o<<" ";
    o<<p[i].first;
  }
  return o;
}

double slice(polygon p,double z){
  set<double> xs;
  for(int i=0;i<p.size();i++){
    double s,t;
    if(edge_cross_edge(p[i],s,edge(cplx(0,z),cplx(1,0)),t)){
      if(0<=s && s<=1){
	xs.insert(real(p[i].first+s*p[i].second));
      }
    }
  }
  assert(xs.size()%2==0);
  set<double>::iterator it,jt;
  jt=xs.begin();
  it=jt++;
  double sum=0;
  for(;;){
    sum+=*jt-*it;
    it++;it++;
    if(it==xs.end())break;
    jt++;jt++;
  }
  //cout << "slice length of " << p << " at " << z <<  " is " << sum <<endl;
  return sum;
}

double volume(polygon p){
  set<double> zs;
  set<double>::iterator it,jt;
  for(int i=0;i<p.size();i++)
    zs.insert(imag(p[i].first));
  
  for(;;){
    bool sw=false;
    jt=zs.begin();
    it=jt++;
    for(;jt!=zs.end();it++,jt++){
      if(abs(*jt-*it)<=epsilon){
	zs.erase(it);
	sw=true;
	break;
      }
    }
    if(!sw)break;
  }
  
  jt=zs.begin();
  it=jt++;
  double sum=0;
  const double div=0.001;
  for(;jt!=zs.end();it++,jt++){
    double zb=*jt,za=*it;
    int divisionNum=(int)((zb-za)/div+5);
    double divisionThickness=(zb-za)/divisionNum;
    for(int i=0;i<divisionNum;i++){
      double slicez=divisionThickness*(i+0.5)+za;
      sum+= divisionThickness * pow(slice(p,slicez),2);
    }
  }
  return sum;
}

vertices normalize(vertices vs){
  vertices ret;
  for(int i=0;i<vs.size();i++){
    int 
      j=(i+1)%vs.size(),
      k=(i+2)%vs.size();
    if(abs(imag((vs[k]-vs[j])*conj(vs[j]-vs[i])))<epsilon)
      /*points i,j,k are on a line*/;
    else
      ret.push_back(vs[j]);
  }
  return ret;
}

int main(){
  ifstream cin("I.txt");
  for(;;){
    int n;
    cin >> n;
    if(n==0)break;
    vertices vs;
    for(int i=0;i<n;i++){
      double x,y;
      cin >> x >> y;
      vs.push_back(cplx(x,y));
    }
    vs=normalize(vs);

    polygon smaller,small,middle,big,bigger;
    for(int i=0;i<vs.size();i++){
      int j=(i+1)%vs.size();
      middle.push_back(edge(vs[i],vs[j]-vs[i]));
    }
    const double thickness=0.005;
    bigger=thicken(middle,2*thickness);
    big=thicken(middle,thickness);
    small=thicken(middle,-thickness);
    smaller=thicken(middle,-2*thickness);

    double
      ans1= (volume(big)-volume(small))/(2*thickness),
      ans2= (volume(bigger)-volume(smaller))/(4*thickness),
      ans = (4.0 * ans1 - ans2)/3.0;
    
    cout << setiosflags(ios::fixed) << setprecision(5) << ans << endl;
  }
  return 0;
}