Merge continuous ranges

SQL> select * from test;

ID S E
---------- ---------- ----------
1 1 5
1 5 7
1 8 12
1 12 19

SELECT ID, MIN (x), MAX (x)
FROM (SELECT CEIL (ROWNUM / 2) rn, ID, x
FROM ((SELECT ID, s x
FROM TEST
MINUS
SELECT ID, e x
FROM TEST)
UNION
(SELECT ID, e x
FROM TEST
MINUS
SELECT ID, s x
FROM TEST)))
GROUP BY ID, rn


ID MIN(X) MAX(X)
---------- ---------- ----------
1 8 19
1 1 7