#include <iostream>
#include <fstream>
#include <utility>
#include <set>
#include <map>
#include <cmath>

using namespace std;

const double PI = 3.1415926535;

typedef pair<int, int> xy;
typedef int flag; // 0x01 (0,0) 0x02 (0,1) 0x04 (1,0) 0x08 (1,1)

const int topleft = 0x01;
const int topright = 0x02;
const int bottomleft = 0x04;
const int bottomright = 0x08;

#define m_(x,y) make_pair(x,y)

int main(void)
{
  ifstream ifs("circle.txt");
  int n;
  int nc = 0;
  while(ifs >> n)
    {
    if(n == 0) break;
    set<xy> points;
    map<xy, flag> grids;
    for(int i = 0; i < n; i++){
      int x, y;
      ifs >> x >> y;
      points.insert(m_(x,y));
      grids[m_(x-1, y-1)] |= bottomright;
      grids[m_(x  , y-1)] |= bottomleft;
      grids[m_(x-1, y  )] |= topright;
      grids[m_(x  , y  )] |= topleft;
    }
    double area = 0.;
    for(map<xy, flag>::iterator it = grids.begin();
        it != grids.end();
        it++)
      {
        switch(it -> second){
        case 0x00:
          area += 0.;
          break;
        case 0x01:
        case 0x02:
        case 0x04:
        case 0x08:
          area += PI / 4.;
          break;
        case 0x03:
        case 0x05:
        case 0x0a:
        case 0x0c:
          area += sqrt(3.) /4. + PI / 6.;
          break;
        default:
          area += 1.;
        }
      }
    if(nc != 0)
      printf("\n");
    printf("Data set #%d:  Total area = %.4f square meters.\n", nc+1, area);
    nc ++;
  }

}