how many days have there been since patient 52898 first received a prescription for famotidine during the current hospital visit?
select 1 * ( strftime('%j',current_time) - strftime('%j',prescriptions.startdate) ) from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 52898 and admissions.dischtime is null ) and prescriptions.drug = 'famotidine' order by prescriptions.startdate asc limit 1