public class Main {

public static void main(String[] args) {

double pi = 0;

for (double i = 1; i < 1000000; i += 4) {

pi=pi+(1/i);}

for(double a=3;a<1000000;a+=4) {

pi=pi-1/a;

}

pi=4*pi;

System.out.println(pi);

}

}