Xiaoqiang practiced addition calculations. When he added from 1 to a certain number, the sum was 1993, but he found that one number was missing in the calculation. What is the missing number?
小强练习加法计算，他从1加到某个数时，和是1993，但他发现计算时少加了一个数，小强少加了的那个数是多少．
<gadget id="calculator">2_016 - 1_993</gadget>
<output>23</output>

<result>23</result>