with t(req, cnt) as 
(
select 1, 3 from dual 
union all select 2, 3 from dual
union all select 3, 3 from dual
union all select 4, 3 from dual
union all select 5, 2 from dual
union all select 6, 2 from dual
union all select 7, 2 from dual
union all select 8, 2 from dual
union all select 9, 2 from dual
union all select 10, 1 from dual
union all select 11, 1 from dual
union all select 12, 1 from dual
union all select 13, 1 from dual
union all select 14, 1 from dual
union all select 15, 1 from dual
)
select bkt, req, cnt
  from (select row_number() over (order by decode(cnt, 2, null, rn), cnt desc) ord, t0.*
          from (select t.*, row_number() over (partition by cnt order by req) rn from t) t0)
match_recognize
(
  order by ord
  measures
    match_number() bkt
  all rows per match
  pattern (x+)
  define
    x as sum(cnt) <= 4
)