40 students line up in two columns on average, with a distance of 1 meter between the front and back, how long is the line?
40个同学平均排成两路纵队，前后两人之间相距1米，这个队伍长多少米．
<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<gadget id="calculator">20 - 1</gadget>
<output>19</output>

<gadget id="calculator">19 * 1</gadget>
<output>19</output>

<result>19</result>