Sum of digits

The sum of the numbers from 0 to $n$ is easy to compute with the formula $n(n+1)/2$. That is, $0 + 1 + 2 + \cdots + n = n(n+1)/2$.

This problem is a little harder. What is the sum of the digits that appear in the sequence $[0, 1, \ldots, n]$?

Write a program that computes the sum of every digit seen while counting from 0 to $n$.

For $n = 15$ you add up the digits appearing in the sequence $[0, 1, 2, \ldots, 14, 15]$. The result is $1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 1 + 0 + 1 + 1 + 1 + 2 + 1 + 3 + 1 + 4 + 1 + 5 = 66$.

A single line with an integer $n$ ($1 \le n \le 10^{16}$).

Print the sum of the digits in the sequence $[0, 1, \ldots, n-1, n]$ on a single line.