instruction: what is the four, the most frequent input event in 2102?
response: SELECT d_items.label FROM d_items WHERE d_items.itemid IN (SELECT t1.itemid FROM (SELECT inputevents_cv.itemid, DENSE_RANK() OVER (ORDER BY COUNT(*) DESC) AS c1 FROM inputevents_cv WHERE STRFTIME('%y', inputevents_cv.charttime) = '2102' GROUP BY inputevents_cv.itemid) AS t1 WHERE t1.c1 <= 4)