what is the last rdw in patient 3277 since 05/2104?
select labevents.valuenum from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 3277 ) and labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'rdw' ) and strftime('%y-%m',labevents.charttime) >= '2104-05' order by labevents.charttime desc limit 1