The school holds a gala, and it is necessary to install colored lights around the square playground, with one set in each of the four corners, and seven lights on each side. How many colored lights should be prepared in total?
学校开联欢晚会，要在正方形的操场四周装彩灯，四个角都装一盏，每边装7盏，那么一共要准备多少盏彩灯？
<gadget id="calculator">4 * 7</gadget>
<output>28</output>

<gadget id="calculator">28 - 4</gadget>
<output>24</output>

<result>24</result>