/** GOKURI */
#include <iostream>
#include <fstream>
#include <vector>
#include <string>
#include <map>
#include <algorithm>
#include <set>
#include <cstdio>
#include <cstdlib>
#include <climits>
#include <cmath>
#include <complex>
#include <iomanip>
using namespace std;

#define FNAME "circle2.txt"
#define cin fin
typedef complex<double> dcomp;

static const int  NUM = 4000;
static const double D = 10.0 / NUM;


double solve( const vector<dcomp>& cs )
{
  vector< vector<double> > pixel( NUM, vector<double>(NUM) );

  // TODO
  for (int i = 0; i < cs.size(); ++i ) {
    int x = int(cs[i].real() / D + 0.5);
    int y = int(cs[i].imag() / D + 0.5);

    for (int j = x - NUM / 10; j != x + NUM / 10; ++j) {
      double xx = j * D - cs[i].real();
      int dy = int(sqrt(1 - xx * xx) / D + 0.5);
      // cout << dy << endl;
      for (int k = 0; k < dy; ++k) {
        pixel[j][y + k] = 1;
        pixel[j][y - k] = 1;
      }
      if((pixel[j][y + dy] += .7) > 1.0)
        pixel[j][y + dy] = 1.0;
      if((pixel[j][y - dy] += .7) > 1.0)
        pixel[j][y - dy] = 1.0;
      //pixel[j][y - dy] += .4;
    }
  }
  
  double cnt = 0;
  for(int i=0; i!=NUM; ++i)
    for(int j=0; j!=NUM; ++j) {
      cnt += pixel[i][j];
    }
  // cout << cnt << endl;
  return double(cnt)*D*D;
}

int main()
{
  ifstream fin(FNAME);
  if(!fin) return -1;

  for(int n; cin>>n,n; )
    {
      vector<dcomp> cs;
      while(n--)
        {
          double x,y;
          cin >> x >> y;
          cs.push_back( dcomp(x,y) );
        }

      cout
        << setiosflags(ios::fixed) << setprecision(2)
        << solve(cs) << endl;
    }
  return 0;
}