#include <iostream>
#include <cstdio>
#include <fstream>	
#include <vector>
#include <set>

using namespace std;

#define M_PI 3.1415926535
#define FNAME "circle.txt"
#define cin fin

ifstream fin(FNAME);

class Point {
public:
	int x, y;

	Point() {}
	Point( int x, int y ) : x(x), y(y) {}

	bool operator < ( const Point &p ) const {
		if ( x < p.x ) return true;
		if ( x > p.x ) return false;
		return (y < p.y);
	}

};



int p1, p2a, p2b, p3, p4;

bool existPoint( const set<Point> &S, int x, int y ) {
	return (S.find(Point(x, y)) != S.end());
}

void count( bool lu, bool lb, bool ru, bool rb ) {
	int non = 0;
	if ( lu ) non++;
	if ( lb ) non++;
	if ( ru ) non++;
	if ( rb ) non++;

	if ( non == 1 )
		p1++;
	else if ( non == 3 )
		p3++;
	else if ( non == 4 )
		p4++;
	else if ( lb && ru || lu && rb )
		p2b++;
	else
		p2a++;
}

void compute( const Point &p, const set<Point> &S ) {
	const int x = p.x;
	const int y = p.y;
	count(existPoint(S, x-1, y+1), existPoint(S, x-1, y), existPoint(S, x, y+1), existPoint(S, x, y));
	count(existPoint(S, x-1, y), existPoint(S, x-1, y-1), existPoint(S, x, y), existPoint(S, x, y-1));
	count(existPoint(S, x, y+1), existPoint(S, x, y), existPoint(S, x+1, y+1), existPoint(S, x+1, y));
	count(existPoint(S, x, y), existPoint(S, x, y-1), existPoint(S, x+1, y), existPoint(S, x+1, y-1));
}

int main() {
	int npoint;

	const double a1 = M_PI/4;
	const double a2a = sqrt(3.0)/4 + M_PI/6;
	const double a2b = 1.0;
	const double a3 = 1.0;
	const double a4 = 1.0;

	for ( int n = 1; cin >> npoint && npoint != 0; n++ ) {
		vector<Point> P;
		set<Point> S;
		Point p;

		for ( int i = 0; i < npoint; i++ ) {
			cin >> p.x >> p.y;
			P.push_back(p);
			S.insert(p);
		}

		p1 = p2a = p2b = p3 = p4 = 0;
		for ( int i = 0; i < npoint; i++ ) compute(P[i], S);

		p2a /= 2;
		p2b /= 2;
		p3 /= 3;
		p4 /= 4;

		const double area = p1*a1 + p2a*a2a + p2b*a2b + p3*a3 + p4*a4;

		if ( n > 1 ) printf("\n");
		printf("Data set #%d:  Total area = %.4lf square meters.\n", n, area);
	}

	return 0;
}