tell me the length of time of patient 8324's last stay in icu.
select strftime('%j',icustays.outtime) - strftime('%j',icustays.intime) from icustays where icustays.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 8324 ) and icustays.outtime is not null order by icustays.intime desc limit 1