  typename EK::Plane_3 read_plane(std::istream& in) {
    typename K::RT a, b, c, d;
    in >> a >> b >> c >> d;
    return typename EK::Plane_3(a, b, c, d);
  }
  typename EK::Plane_3 read_plane(std::istream& in) {
    typename K::RT a, b, c, d;
    in >> a >> b >> c >> d;
    return typename EK::Plane_3(a, b, c, d);
  }