instruction: what is patient 015-67291's length of stay in the icu for the last time?
response: SELECT STRFTIME('%j', patient.unitdischargetime) - STRFTIME('%j', patient.unitadmittime) FROM patient WHERE patient.patienthealthsystemstayid IN (SELECT patient.patienthealthsystemstayid FROM patient WHERE patient.uniquepid = '015-67291') AND NOT patient.unitadmittime IS NULL ORDER BY patient.unitadmittime DESC LIMIT 1