Xiaodong counts, counting from 9 to 99, how many numbers does Xiaodong count.
小东数数，从9开始数起，数到99时，小东数了多少个数．
<gadget id="calculator">99 - 9</gadget>
<output>90</output>

<gadget id="calculator">90 + 1</gadget>
<output>91</output>

<result>91</result>