How to find out top enqeue waits ??? top enqueue sql ( top contention )

set lines 182 pages 5000
col event format a35
SELECT sql_id,
  event,
  p1,
  mod(p1,16) AS "mode",
  SUM(TIME_WAITED) T_waited
FROM gv$active_session_history
WHERE event LIKE 'enq%' and sql_id is not null
GROUP BY sql_id,
  event,
  p1,
  mod(p1,16) order by 5 desc;