Rank (Node p k l r) = realRank l >= realRank r && k == 1 + realRank l + realRank r


okRank (Node p k l r) = realRank l >= realRank r && k == 1 + realRank l + realRank r
okRank (Node p k l r) = realRank l >= realRank r && k == 1 + realRank l + realRank r