instruction: what was the drug which in 08/2102 had been prescribed to patient 6440 two times?
response: 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 = 6440) AND STRFTIME('%y-%m', prescriptions.startdate) = '2102-08' GROUP BY prescriptions.drug) AS t1 WHERE t1.c1 = 2