A rope 2 meters long, cut off 1 decimeter, how many decimeters are left.
一根长2米的绳子，剪去1分米，还剩多少分米．
<gadget id="calculator">2 * 10</gadget>
<output>20</output>

<gadget id="calculator">20 - 1</gadget>
<output>19</output>

<result>19</result>