instruction: how many patients who are diagnosed with short title encephalopathy nos have been prescibed additive type of drug?
response: SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic INNER JOIN diagnoses ON demographic.hadm_id = diagnoses.hadm_id INNER JOIN prescriptions ON demographic.hadm_id = prescriptions.hadm_id WHERE diagnoses.short_title = "Encephalopathy NOS" AND prescriptions.drug_type = "ADDITIVE"