#include <iostream>
#include <fstream>
#include <cstdio>
#include <cmath>
#include <vector>
#include <utility>
using namespace std;

#define foreach(T, p, c) for(T p = (c).begin(); p != (c).end(); ++p)
typedef pair<int, int> point;
#define XX first
#define YY second

double SUnit[4];
vector<point> V;

double size(int x, int y, int vx, int vy){
  bool X[4];
  int cnt = 0;
  X[0] = false;
  X[1] = false;
  X[2] = false;
  X[3] = false;
  int r = ((vx == 1) ? 1 : 0);
  int b = ((vy == 1) ? 1 : 0);
  int l = 1 - r;
  int t = 1 - b;
  foreach(vector<point>::iterator, q, V){
    if      (q->XX == x + l && q->YY == y + t){
      X[0] = true;
      cnt++;
    }else if(q->XX == x + l && q->YY == y + b){
      X[1] = true;
      cnt++;
    }else if(q->XX == x + r && q->YY == y + t){
      X[2] = true;
      cnt++;
    }else if(q->XX == x + r && q->YY == y + b){
      X[3] = true;
      cnt++;
    }
  }
  if(cnt == 0){
    //cout << SUnit[0] << endl;
    return SUnit[0];
  }else if(cnt == 1){
    //cout << SUnit[1] << endl;
    return SUnit[1];
  }else if(cnt >= 3){
    // cout << r << "," << b << "," << cnt << endl;
    //cout << SUnit[3] << endl;
    return SUnit[3] / cnt;
  }else if(X[0] && X[3]){
    //cout << SUnit[3] << endl;
    return SUnit[3] / cnt;
  }else if(X[1] && X[2]){
    //cout << SUnit[3] << endl;
    return SUnit[3] / cnt;
  }else{
    //cout << SUnit[2] << endl;
   return SUnit[2] / cnt;
  }
}

int main(){
  int N;
  SUnit[0] = 0.0;
  SUnit[1] = M_PI / 4.0;
  SUnit[2] = (M_PI / 6.0) + (sqrt(3.0) / 4.0);
  SUnit[3] = 1.0;

  ifstream cin("circle.txt");

  for(int iii=1; cin >> N ; iii++){
    if(N == 0){ break; }
    V.clear();
    for(int i=0; i<N; i++){
      int x, y;
      cin >> x >> y;
      V.push_back(make_pair(x,y));
    }
    double S = 0;
    foreach(vector<point>::iterator, p, V){
      // cout << "#" << p->XX << p->YY << endl;
      S += size(p->XX-1, p->YY-1, 1, 1);
      S += size(p->XX-1, p->YY,   1, 0);
      S += size(p->XX,   p->YY-1, 0, 1);
      S += size(p->XX,   p->YY,   0, 0);
    }
    if(iii > 1){ printf("\n"); }
    printf("Data set #%d:  Total area = %.4f square meters.\n", iii, S);
  }
}