According to reports, the invention patent of disposable wooden chopsticks belongs to Japan, and the consumption of disposable wooden chopsticks in Japan also ranks first in the world, but Japan itself never produces this kind of product, and all of them are imported from abroad. China exports 20 billion pairs of high-quality wooden chopsticks to Japan every year, and 20,000 cubic meters of wood are used to manufacture 100 million pairs of wooden chopsticks, and each cubic meter of wood is equivalent to about 4 large trees. May I ask China to export to Japan every year? 20 billion pairs of wooden chopsticks, how many trees need to be cut down?
据报道，一次性木筷的发明专利属于日本n，日本国内一次性木筷的消耗量也名列世界第一，但日本自己却从不生产这种产品，全部从国外进口．中国每年向日本出口200亿双优质木筷，而每制造1亿双木筷就要用去0.2万立方米的木材，而每立方米木材大约相当于4棵大树，请问中国每年向日本出口200亿双木筷，需要砍去多少棵大树？
<gadget id="calculator">400_000 * 4</gadget>
<output>1_600_000</output>

<result>1_600_000</result>