package main;

public class ApproximatePI 
{

	public static void main(String[] args)
	{
		System.out.println((4 * (1.0 - (1.0 / 3) + (1.0 / 5) - (1.0 / 7) + (1.0 / 9) - (1.0 / 11) + (1.0 / 13))));
	}

}