In a cold drink shop, a bottle of soda is 1 yuan. After drinking the soda, you can exchange 2 empty bottles for 1 soda. If you have 20 yuan, how many bottles of soda can you drink at most?
一家冷饮店，一瓶汽水1元钱，喝完汽水后，用2个空瓶可以换1瓶汽水，若你有20元钱，最多可以喝到几瓶汽水？
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">20 + 10 + 5 + 2 + 1 + 1 + 1</gadget>
<output>40</output>

<result>40</result>