import java.awt.*;
import static java.lang.Math.*;
import javax.swing.*;

public class XiaolinWu extends JPanel {

    public XiaolinWu() {
        Dimension dim = new Dimension(640, 640);
        setPreferredSize(dim);
        setBackground(Color.white);
    }

    void plot(Graphics2D g, double x, double y, double c) {
        g.setColor(new Color(0f, 0f, 0f, (float)c));
        g.fillOval((int) x, (int) y, 2, 2);
    }

    int ipart(double x) {
        return (int) x;
    }

    double fpart(double x) {
        return x - floor(x);
    }

    double rfpart(double x) {
        return 1.0 - fpart(x);
    }

    void drawLine(Graphics2D g, double x0, double y0, double x1, double y1) {

        boolean steep = abs(y1 - y0) > abs(x1 - x0);
        if (steep)
            drawLine(g, y0, x0, y1, x1);

        if (x0 > x1)
            drawLine(g, x1, y1, x0, y0);

        double dx = x1 - x0;
        double dy = y1 - y0;
        double gradient = dy / dx;