instruction: what is the number of patients whose age is less than 43 and diagnoses long title is other preterm infants, 750-999 grams?
response: SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic INNER JOIN diagnoses ON demographic.hadm_id = diagnoses.hadm_id WHERE demographic.age < "43" AND diagnoses.long_title = "Other preterm infants, 750-999 grams"