Prepare to plant colorful flags around the square site of the celebration. If a colorful flag is to be inserted on the four corners, there must be 7 colored flags on each side. So how many flags are there in total?
在正方形的庆功大会的场地周围准备插上彩旗．如果四个角上都要插上一面彩旗，要使每边有7面彩旗．那么一共要准备多少面彩旗？
<gadget id="calculator">7 * 4</gadget>
<output>28</output>

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

<result>24</result>