The school holds a reading competition, and the prescribed reading time is 4 minutes. Dongdong reads 117 characters per minute, and his manuscript has a total of 520 characters. How many characters should he delete at least?
学校举行朗读比赛，规定朗读时间为4分钟．东东每分钟读117个字，他的稿子共520个字，他最少要删掉多少个字？
<gadget id="calculator">117 * 4</gadget>
<output>468</output>

<gadget id="calculator">520 - 468</gadget>
<output>52</output>

<result>52</result>