package com.company;

//p/8 = 1/1*3 + 1/5*7 - 1/9*11+...
public class Main {

    public static void main(String[] args) {
        final double e = 0.0000000000001;
        int i = 1;
        double p0 = 0;
        double p1 = 0;
        double sum = 0;
        do {
            p1 = p0;
            p0 = (double) 1 / (i * (i + 2));
            sum += p0;
            i += 4;
        } while (Math.abs(p1 - p0) > e);
        System.out.println(sum * 8);
    }
}