On both sides of the corridor of the school, put a box of flowers every 4 meters, a total of 18 boxes are placed, and there is a pot of flowers at the beginning and end. How long is this corridor?
在学校的走廊两边，每隔4米放1盒花，一共放了18盒，且起点和终点各有1盆花，这条走廊长多少米？
<gadget id="calculator">18 / 2</gadget>
<output>9</output>

<gadget id="calculator">9 - 1</gadget>
<output>8</output>

<gadget id="calculator">8 * 4</gadget>
<output>32</output>

<result>32</result>