Xiaodong participated in the swimming competition and swam 4 back and forth on the 50-meter-long swimming lane. Do you know how many meters he raced?
小东参加游泳比赛，在50米长的泳道上游了4个来回．你知道他参加的是多少米的比赛吗？
<gadget id="calculator">50 * 2 * 4</gadget>
<output>400</output>

<result>400</result>