using System;

public class Program

{

    public static void Main()

    {

        double pi = 0 ;

        double pi_was = 1;

        double teller =1;

        while(pi != pi_was)

        {

            pi_was = pi;

            pi = pi + 1/teller - 1/(teller+2);

            teller = teller+4;

        }

        Console.WriteLine("Pi is " + 4*pi);

    }

}