in total, count the number of times patient 15945 had been prescribed atorvastatin in 12/this year.
select count(*) from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 15945 ) and prescriptions.drug = 'atorvastatin' and datetime(prescriptions.startdate,'start of year') = datetime(current_time,'start of year','-0 year') and strftime('%m',prescriptions.startdate) = '12'