give me the difference between the total amount of input and the output for patient 21468 on 03/25/this year.
select ( select sum(inputevents_cv.amount) from inputevents_cv where inputevents_cv.icustay_id in ( select icustays.icustay_id from icustays where icustays.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 21468 ) ) and datetime(inputevents_cv.charttime,'start of year') = datetime(current_time,'start of year','-0 year') and strftime('%m-%d',inputevents_cv.charttime) = '03-25' ) - ( select sum(outputevents.value) from outputevents where outputevents.icustay_id in ( select icustays.icustay_id from icustays where icustays.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 21468 ) ) and datetime(outputevents.charttime,'start of year') = datetime(current_time,'start of year','-0 year') and strftime('%m-%d',outputevents.charttime) = '03-25' )