tell me the first glucose in patient 40435 in 12/2105?
select labevents.valuenum from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 40435 ) and labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'glucose' ) and strftime('%y-%m',labevents.charttime) = '2105-12' order by labevents.charttime asc limit 1