  Using unknotting number, we introduce a link diagram invariant of Hass and
Nowik type, which changes at most by 2 under a Reidemeister move.
  As an application, we show that a certain infinite sequence of diagrams of
the trivial two-component link need quadratic number of Reidemeister moves for
being unknotted with respect to the number of crossings.
  Assuming a certain conjecture on unknotting numbers of a certain series of
composites of torus knots, we show that the above diagrams need quadratic
number of Reidemeister moves for being splitted.
