///gnc
#include <iostream>
#include <fstream>
#include <vector>
#include <complex>
#include<iomanip>

using namespace std;

#define MAGNIFIER 200

typedef complex<double> xy;

int main(void)
{
  ifstream is("circle2.txt");
  int n;
  while(is >> n && n){
    vector<xy> pts;
    for(int i=0; i < n; i++){
      double x, y;
      is >> x >> y;
      pts.push_back(xy(x * MAGNIFIER,  y * MAGNIFIER));
    }
    int area = 0;
    for(int x = 0 * MAGNIFIER; x < 10 * MAGNIFIER; x++){
      for(int y = 0 * MAGNIFIER; y < 10 * MAGNIFIER; y++){
        xy p((double)x, (double)y);
        bool b = false;
        for(int i =0; i < n; i++){
          if(abs(p - pts[i]) < (MAGNIFIER)){
            b = true;
          }
        }
        if(b) area++;
      }
    }
    printf("%.2f\n" , (double)area / MAGNIFIER / MAGNIFIER);
  }
  return 0;
}