Amin did a little experiment while drinking tea. He inserted a chopstick straight into the bottom of the cup, and he measured that the length of the part soaked by water was 10 cm. He turned the chopsticks around and inserted the other end straight into the bottom of the cup. At this time, he found that the dry part of the chopsticks was 10 cm shorter than the wet part. So how many centimeters is this chopstick long?
阿明在喝茶的时候做了一个小实验．他把一根筷子笔直的插到杯底，他量了一下被水浸湿部分的长度是10厘米．他把筷子掉个头，将另一端笔直的插到杯底，这时候他发现，筷子干的部分比湿的部分短10厘米．那麽这根筷子长多少厘米？
<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<gadget id="calculator">20 - 10</gadget>
<output>10</output>

<gadget id="calculator">20 + 10</gadget>
<output>30</output>

<result>30</result>