An electric car is running on a 400-meter-long runway, and its speed is: 2 meters in the first second, 3 meters in the second second, 2 meters in the third second, 3 meters in the fourth second, ..., and so on. How many seconds does it take for the electric car to travel from the start to the end of the track.
电动车在长400米的跑道上行驶，其速度规律为：第一秒行2米，第二秒行3米，第三秒行2米，第四秒行3米，…，依此类推，电动车从跑道起点行驶到终点需多少秒．
<gadget id="calculator">2 + 3</gadget>
<output>5</output>

<gadget id="calculator">400 / 5</gadget>
<output>80</output>

<gadget id="calculator">80 * 2</gadget>
<output>160</output>

<result>160</result>