declare @t table(k int primary key, v int)
insert into @t
values (0, null), (1, -1), (2, 1), (3, 2), (4, 2), (5, 7), (6, 8), (7, 4), (8, 1), (9, 3), (10, 0), (11, 8), (12, 9), (13, 10), (14, 11);

with A as
(select this_k = max(case when e.x  = (b.r % 2) then b.k end),
        this_v = max(case when e.x  = (b.r % 2) then b.v end),
        next_v = max(case when e.x != (b.r % 2) then b.v end)
   from (select a.v, a.k, row_number() over(order by a.k) as r
           from @t as a) as b
          cross join (select 0 as x union all select 1 as x) as e
  group by b.r + case when e.x = (b.r % 2) then 1 else 0 end
/*  order by this_k
 offset 1 rows
*/)
 
select this_k, this_v, next_v
  from A
 where this_k is not null