#include <iostream>
#include <cstdio>
#include <fstream>

using namespace std;

#define NPOINT_MAX 10
#define DEPTH_MAX 13
#define FACTOR 0.68

class Point {
public:

	double x, y;

	double sqdist( double px, double py ) {
		return (px-x)*(px-x) + (py-y)*(py-y);
	}

};


int ncircle;
Point C[NPOINT_MAX];

bool overlapped( double x, double X, double y, double Y ) {
	for ( int i = 0; i < ncircle; i++ ) {
		const double cx = C[i].x, cy = C[i].y;

		if ( cx <= x-1 || cx >= X+1 ) continue;
		if ( cy <= y-1 || cy >= Y+1 ) continue;

		if ( x <= cx && cx <= X || y <= cy && cy <= Y ) return true;
		if ( C[i].sqdist(x,y) < 1 ) return true;
		if ( C[i].sqdist(X, y) < 1 ) return true;
		if ( C[i].sqdist(x, Y) < 1 ) return true;
		if ( C[i].sqdist(X, Y) < 1 ) return true;
	}

	return false;
}

bool involved( double x, double X, double y, double Y ) {
	for ( int i = 0; i < ncircle; i++ ) {
		if ( C[i].sqdist(x, y) > 1 ) continue;
		if ( C[i].sqdist(X, y) > 1 ) continue;
		if ( C[i].sqdist(x, Y) > 1 ) continue;
		if ( C[i].sqdist(X, Y) > 1 ) continue;
		return true;
	}

	return false;
}

double compute( double x, double X, double y, double Y, int depth ) {
	if ( !overlapped(x, X, y, Y) ) return 0.0;

	// 十分小さいので入っていることにする. FACTOR の微調整が必要.
	if ( depth == DEPTH_MAX ) return (X-x)*(Y-y)*FACTOR;

	// 完全に入っている場合.
	if ( involved(x, X, y, Y) ) return (X-x)*(Y-y);

	double result = 0.0;
	result += compute(x, (X+x)/2, y, (Y+y)/2, depth+1);
	result += compute(x, (X+x)/2, (Y+y)/2, Y, depth+1);
	result += compute((X+x)/2, X, y, (Y+y)/2, depth+1);
	result += compute((X+x)/2, X, (Y+y)/2, Y, depth+1);
	return result;
}

int main() {
	ifstream cin("circle2.txt");

	while ( cin >> ncircle, ncircle ) {
		for ( int i = 0; i < ncircle; i++ ) cin >> C[i].x >> C[i].y;
		printf("%.2lf\n", compute(0.0, 10.0, 0.0, 10.0, 0));
	}

	return 0;
}