The lanes of the swimming pool arranged by the school are 50 meters long, and Haoran has to swim a total of 500 meters. He has already swam three rounds, how many more rounds will he have to swim?
学校安排的游泳池泳道长50米，浩然一共要游500米，他已经游了3个来回，还要游几个来回？
<gadget id="calculator">50 * 2 * 3</gadget>
<output>300</output>

<gadget id="calculator">500 - 300</gadget>
<output>200</output>

<gadget id="calculator">50 * 2</gadget>
<output>100</output>

<gadget id="calculator">200 / 100</gadget>
<output>2</output>

<result>2</result>