[{data:[1,0,4,0,0,4,1,3,0,1,0,2,2,0,1,1,0,2,0,4,1,1,0,1,1,0]}]

db.collection.aggregate([{$project:{"_id":0,"data":{"$slice":["$data",0,{$subtract:[{$size:"$data"},3]}]}}}])