what is the drug that in their first hospital encounter patient 61751 has been prescribed two times?
select t1.drug from ( select prescriptions.drug, count( prescriptions.startdate ) as c1 from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 61751 and admissions.dischtime is not null order by admissions.admittime asc limit 1 ) group by prescriptions.drug ) as t1 where t1.c1 = 2