Put colored flags around a square field, one at each of the four corners, and 18 on each side, how many colored flags are there in total?
在一个正方形场地四周插彩旗，四个角都插一面，每条边插了18面，这个场地共插了多少面彩旗？
<gadget id="calculator">18 * 4</gadget>
<output>72</output>

<gadget id="calculator">72 - 4</gadget>
<output>68</output>

<result>68</result>