Dongdong has 5 pencils, Nannan has 9 pencils, how many more can Dongdong buy as many as Nannan?
冬冬有5支铅笔，南南有9支铅笔，冬冬再买几支就和南南的一样多？
<gadget id="calculator">9 - 5</gadget>
<output>4</output>

<result>4</result>