Tiantian learns to count: 1, 2, 3, 4, ... count down one by one until 100, how many natural numbers did she count including the number 5?
甜甜学数数：1、2、3、4、…一个接一个地往下数，一直数到100，她一共数了多少个含有数字5的自然数．
<gadget id="calculator">10 + 9</gadget>
<output>19</output>

<result>19</result>