instruction: give me the difference between patient 7698's total input and the total output on last month/04?
response: 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 = 7698)) AND DATETIME(inputevents_cv.charttime, 'start of month') = DATETIME(CURRENT_TIME(), 'start of month', '-1 month') AND STRFTIME('%d', inputevents_cv.charttime) = '04') - (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 = 7698)) AND DATETIME(outputevents.charttime, 'start of month') = DATETIME(CURRENT_TIME(), 'start of month', '-1 month') AND STRFTIME('%d', outputevents.charttime) = '04')