instruction: find the number of patients whose diagnoses title is chrn chpt c wo hpat coma and drug type is main.
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 = "Chrnc hpt C wo hpat coma" AND prescriptions.drug_type = "MAIN"