instruction: in 2105 what are the four most frequent medications prescribed during the same hospital encounter to the patients of age 50s after being diagnosed with long-term use of insulin?
response: SELECT t3.drug FROM (SELECT t2.drug, DENSE_RANK() OVER (ORDER BY COUNT(*) DESC) AS c1 FROM (SELECT admissions.subject_id, diagnoses_icd.charttime, admissions.hadm_id FROM diagnoses_icd JOIN admissions ON diagnoses_icd.hadm_id = admissions.hadm_id WHERE diagnoses_icd.icd9_code = (SELECT d_icd_diagnoses.icd9_code FROM d_icd_diagnoses WHERE d_icd_diagnoses.short_title = 'long-term use of insulin') AND STRFTIME('%y', diagnoses_icd.charttime) = '2105') AS t1 JOIN (SELECT admissions.subject_id, prescriptions.drug, prescriptions.startdate, admissions.hadm_id FROM prescriptions JOIN admissions ON prescriptions.hadm_id = admissions.hadm_id WHERE admissions.age BETWEEN 50 AND 59 AND STRFTIME('%y', prescriptions.startdate) = '2105') AS t2 ON t1.subject_id = t2.subject_id WHERE t1.charttime < t2.startdate AND t1.hadm_id = t2.hadm_id GROUP BY t2.drug) AS t3 WHERE t3.c1 <= 4