Pi Calculator

package trp.pi;

public class Main {
	public static void main(String[] args){

		double pi = 0;
		double x = 0;

		do{
			x += 4;
			pi += (4 / (x-3)) - (4 / (x-1));
			System.out.println(x + " <- x ..... pi -> " + pi);

		}while(x>-1);

		System.out.println("pi = " + pi);
	}
}