/* calculation of pi: approximating a circle by polygons */
#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;

int main()
{
	int nsides = 6;	double length = 1.;

	for(int i=0;i<27;i++) {

		length = sqrt(2. - sqrt(4. - length*length));
		nsides *= 2;
		double pi = length*(double)nsides/2.;
//        cout << fixed;
		cout <<   setw(10) << nsides << "\t" << setprecision(16) << pi << "\t" << fabs(M_PI-pi) << endl;
	}

}