Definition share_metric (n : nat) (s : canonTree) : nat :=
 match n with
 | 0 => 0
 | S n => match le_dec (height s) n with
          | left _ => countBLeafCT n s + 1
          | right _ => 0
         end
 end.

Lemma leq_dec : forall (x y : t), {(x <= y)%ba} + {~ (x <= y)%ba}.