declare @n bigint, @k bigint;
declare @s varchar(100);

set @n = 111233;
set @s = cast(@n as varchar);
set @k = len(@s);

with cte as
(
    select
		cast(case when substring(@s, 1, 1) = substring(@s, 2, 1) then '' else substring(@s, 1, 1) end as varchar(30)) f,
        2 i
    union all
    select 
		cast(f+case when substring(@s, i, 1) in (substring(@s, i+1, 1), substring(@s, i-1, 1)) then '' else substring(@s, i, 1) end as varchar(30)) f,
        i+1
    from 
        cte
    where 
        i <= @k
)
select max(f) from cte