Junjun ran back and forth 4 times along the 100-meter runway, how many meters did he run in total?
军军沿着100米的跑道跑了4个来回，他一共跑了多少米米．
<gadget id="calculator">4 * 2</gadget>
<output>8</output>

<gadget id="calculator">100 * 8</gadget>
<output>800</output>

<result>800</result>