double bismuth(double x, double y)
{
    double fx = fabs(x), fy = fabs(y), ret = 2.0;
    if ((fx < 1.0) && (fy < 1.0))
        ret = powf(fabs(x + y), 1.0/3.0);
    else if ((fx > 1.0) || (fy > 1.0))
        ret = x*x + x*y + y*y;
    return ret;
}