After a person has walked half of the total length along the Dati, and walked the remaining half, there is still 1 kilometer left. Ask: How many kilometers is the total length of the Dati?
一个人沿着大提走了全长的一半后，又走了剩下的一半，还剩下1千米，问：大提全长多少千米？
<gadget id="calculator">1 * 2 * 2</gadget>
<output>4</output>

<result>4</result>