WITH seat_status AS (
  SELECT 
    LINE_ID,
    SEAT_NO,
    RSV_STATUS,
    LAG(RSV_STATUS, 1) OVER (PARTITION BY LINE_ID ORDER BY SEAT_NO) AS PREV_STATUS_1,
    LAG(RSV_STATUS, 2) OVER (PARTITION BY LINE_ID ORDER BY SEAT_NO) AS PREV_STATUS_2
  FROM SEAT_RESERVE
),
free_seats AS (
  SELECT 
    LINE_ID,
    SEAT_NO AS SEAT_F,
    LEAD(SEAT_NO, 2) OVER (PARTITION BY LINE_ID ORDER BY SEAT_NO) AS SEAT_T
  FROM seat_status
  WHERE RSV_STATUS = '0'
    AND PREV_STATUS_1 = '0'
    AND PREV_STATUS_2 = '0'
)
SELECT 
  LINE_ID AS LINE,
  SEAT_F,
  SEAT_F+2 AS SEAT_T
FROM free_seats
WHERE SEAT_T IS NOT NULL
ORDER BY LINE_ID DESC, SEAT_F ASC;