what was the maximum hemoglobin value for patient 9619 until 05/2102.
select max(labevents.valuenum) from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 9619 ) and labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'hemoglobin' ) and strftime('%y-%m',labevents.charttime) <= '2102-05'