P5965 [PA 2019] A+B

When writing down the vertical addition of two decimal numbers, people may miscalculate it like this:  In the left part of the picture, $248+208$ is wrongly calculated as $4416$. Given a positive integer $n$, ask how many pairs of non-negative integers $a,b$ satisfy that $a+b$ would be miscalculated as $n$. Note that $a$ may be equal to $b$, and $a=1,b=2$ and $a=2,b=1$ are considered two different solutions.

The first line contains a positive integer $n$.

Output an integer, the number of pairs $a,b$ that satisfy the condition.

For $100\%$ of the testdata, $1\le n