Plant trees on one side of a small river with a length of 1000 meters (both ends are planted), and plant a willow tree every 20 meters. How many willow trees are needed in total?
在一条长1000米的小河一边绿化植树(两端都种)，每隔20米种一棵柳树，一共需要多少棵柳树．
<gadget id="calculator">1_000 / 20</gadget>
<output>50</output>

<gadget id="calculator">50 + 1</gadget>
<output>51</output>

<result>51</result>