Finding shorter solution for the grouping

Question

I've got solution for the aggregations I'm looking for, however I believe there is a shorter way to achieve same output with a single query.

The engine is RedShift.

select
    a    
    ,null as b
    ,null as c
    ,sum(fact) as f 
from foo
group by grouping sets(
    a
    , ())
union all
select
    a    
    ,b
    ,null as c
    ,sum(fact) as f 
from foo
group by grouping sets(
    (a,b)
    , (a))
union all
select
    a    
    ,b
    ,c
    ,sum(fact) as f 
from foo
group by grouping sets(
    (a,b,c)
    , (a,b)
)
;

See the SQL sample. A shorter query to achieve the same outcome.