Kaylee needs to sell 33 boxes of biscuits. So far, she has sold 12 boxes of lemon biscuits to her aunt, 5 boxes of chocolate biscuits to her mother, and 4 boxes of oatmeal biscuits to a neighbor. How many more boxes of biscuits does Kaylee need to sell?
Please reason step by step, and put your final answer within \boxed{}.
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