what was the average value of patient 433's potassium in 02/last year?
select avg(labevents.valuenum) from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 433 ) and labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'potassium' ) and datetime(labevents.charttime,'start of year') = datetime(current_time,'start of year','-1 year') and strftime('%m',labevents.charttime) = '02'