There are 20 pots of butterflies in a row at the gate of the school, and 2 pots of chrysanthemums are placed between each two pots of butterflies. How many pots of chrysanthemums are needed in total?
学校门口摆了一排蝴蝶花，共20盆，每两盆蝴蝶花之间插2盆菊花，一共需要多少盆菊花？
<gadget id="calculator">20 - 1</gadget>
<output>19</output>

<gadget id="calculator">19 * 2</gadget>
<output>38</output>

<result>38</result>