void draw_sphere(int n) {
    glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
    glBegin(GL_POLYGON);
    double pi = 3.141591;
    double r = 0.75;
    double step = 2 * pi / n;
    double phi = -pi / 2;
    double theta = 0;
    double phi1;
    for (int i = 0; i < n; ++i) {
        if (i == 0 || n == i - 1) {
            phi1 = phi;
        } else {
            phi1 = phi + step / 2;
            if (phi1 > 2 * pi) {
                phi1 -= 2 * pi;
            }
        }
        for (int j = 0; j < n; ++j) {
            double theta1 = theta + step;
            if (theta1 > 2 * pi) {
                theta1 -= 2 * pi;
            }

            auto sphericToCortesian = [&r](double phi, double theta) -> std::vector<double> {
                return {r * cos(phi) * cos(theta), r * cos(phi) * sin(theta), r * sin(phi)};
            };

            auto p1 = sphericToCortesian(phi, theta);
            auto p2 = sphericToCortesian(phi, theta1);
            auto p3 = sphericToCortesian(phi1, theta);
            auto p4 = sphericToCortesian(phi1, theta1);


            auto drawPoint = [&r](const std::vector<double> &p) {
                static const double light[3] = { 0, 0, -1 };
                double normal[3] = { p[0] / r, p[1] / r, p[2] / r };
                double intens = light[0] * normal[0] + light[1] * normal[1] + light[2] * normal[2];
                glColor3d(intens, intens, intens);
                glVertex3d(p[0], p[1], p[2]);
            };

            drawPoint(p1);
            drawPoint(p2);
            drawPoint(p4);
            drawPoint(p3);

            theta += step;
            if (theta > 2 * pi) {
                theta -= 2 * pi;
            }
        }
        phi += step / 2;
        if (phi > 2 * pi) {
            phi -= 2 * pi;
        }
    }
    glEnd();
}