There is a square playground, 17 trees are planted on each side, and 1 tree in each of the four corners, how many trees are planted in total?
有一正方形操场，每边都栽种17棵树，四个角各种1棵，共种多少棵？
<gadget id="calculator">17 * 4</gadget>
<output>68</output>

<gadget id="calculator">68 - 4</gadget>
<output>64</output>

<result>64</result>