If a person's age in 1984 is exactly equal to the sum of the numbers in his year of birth, then how old was this person in 1984?
1984年某人的岁数正好等于他出生年份的数字之和，那么这人1984年多少岁．
<gadget id="calculator">1_984 - 1_964</gadget>
<output>20</output>

<result>20</result>