what was the name of the drug prescribed to patient 20801, two times until 09/2105?
select t1.drug from ( select prescriptions.drug, count( prescriptions.startdate ) as c1 from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 20801 ) and strftime('%y-%m',prescriptions.startdate) <= '2105-09' group by prescriptions.drug ) as t1 where t1.c1 = 2