4・194 A book has page numbers from 1 to $n$. When the page numbers of this book were added up, one page number was mistakenly added one extra time, resulting in an incorrect sum of 1986. What is the page number that was added one extra time?
[Solution] Let $k$ be the page number that was added one extra time, then $03972,
\end{aligned}
$$

Thus,
$$
n=62 \text{.}
$$

Therefore, $k=1986-\frac{62 \times 63}{2}=33$,
which means the page number that was added one extra time is 33.