The Spring Festival of the Year of the Goat in 2015 is on February 19th, and we found that the number 219 is very special: the two digits composed of the first two digits of this number minus the first digit are just the two digits composed of the last two digits. That is: 21-2=19, we call the number that satisfies this condition a "happy number", so how many "happy numbers" are there in all three-digit numbers?
2015年羊年春节在2月19日，我们发现219这个数很特殊：这个数的前两位数字组成的两位数减去第一位数字，刚好是后两位数字组成的两位数，即：21-2=19，咱们把满足这样条件的数叫做"幸福数"那么所有的三位数中，"幸福数"有多少个？
<gadget id="calculator">2 * 9</gadget>
<output>18</output>

<result>18</result>