Every time half of the toys in the toy store are sold, 20 toys will be replenished. After the tenth half of the toys are sold, there will be exactly 20 remaining toys. How many toys are there in the toy store?
玩具店的玩具每卖出一半就补充20个，到第十次卖出一半后，恰好余下20个，则玩具店原来有玩具多少个．
<gadget id="calculator">20 * 2</gadget>
<output>40</output>

<result>40</result>