###HUMAN: Count the number of patients on a sulfameth/trimethoprim ds prescription who were hospitalized for more than 17 days., ###ASSISTANT: SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic INNER JOIN prescriptions ON demographic.hadm_id = prescriptions.hadm_id WHERE demographic.days_stay > "17" AND prescriptions.drug = "Sulfameth/Trimethoprim DS"