It is stipulated that 10 tons is recorded as 0 tons, and 11 tons is recorded as +1 ton, so how many tons is the weight represented by -1 ton.
规定10吨记为0吨，11吨记为+1吨，则-1吨表示的重量为多少吨．
<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<result>9</result>