how many days have pass since the last time patient 31854 stayed in careunit ccu during the current hospital visit?
select 1 * ( strftime('%j',current_time) - strftime('%j',transfers.intime) ) from transfers where transfers.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 31854 and admissions.dischtime is null ) and transfers.careunit = 'ccu' order by transfers.intime desc limit 1