public class ArchimedesFast {

    public static void main (String[] argv)
    {
	// Radius:
	double r = 8;

	// Number of triangles to inscribe.
	int N = 100;

	// Interior angle of each.
	double angle = 2*Math.PI / N;

	// The corner of the triangle touching the x-axis:
	double x1 = r;
	double y1 = 0;

	// The second corner:
	double x2 = r * Math.cos (angle);
	double y2 = r * Math.sin (angle);

	// Distance between the two:
	double dist = Math.sqrt ((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2));

	// Multiply by N:
	double perimeter = N * dist;

	// The estimate of is the perimeter divided by the diameter:
	double piEstimate = perimeter / (2*r);
	System.out.println ("pi=" + piEstimate);
    }

}