Xiaojun went swimming. He swam back and forth twice in the swimming lane, and swam a total of 200 meters. How long is the swimming lane in this swimming pool?
小军去游泳，他在泳道内游了两个来回，共游了200米，这个游泳池的泳道长多少米．
<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<gadget id="calculator">200 / 4</gadget>
<output>50</output>

<result>50</result>