Champernowne Subsequence

The $k^{\text{th}}$ Champernowne word is obtained by writing down the first $k$ positive integers and concatenating them together. For example, the $10^{\text{th}}$ Champernowne word is $12345678910$.

It can be proven that, for any finite string of digits, there exists some integer $k$ such that the finite string of digits will appear as a subsequence in the $k^{\text{th}}$ Champernowne word.

String $s$ is a subsequence of string $t$ if it is possible to delete some (possibly zero) characters from $t$ to get $s$.

Given a string of digits, compute the smallest integer $k$ such that the given string of digits is a subsequence of the $k^{\text{th}}$ Champernowne word.

The first line of input contains a single integer $n$ $(1 \leq n \leq 10^5)$, the length of the string of digits.

The second line of input contains a string of $n$ digits.

Output a single integer $k$, the minimum integer such that the given string is a subsequence of the $k^{\text{th}}$ Champernowne word.