CF552B.Vanya and Books

Vanya got an important task — he should enumerate books in the library and label each book with its number. Each of the n books should be assigned with a number from 1 to n. Naturally, distinct books should be assigned distinct numbers.

Vanya wants to know how many digits he will have to write down as he labels the books.

万尼亚接到了一项重要任务——他需要为图书馆的图书编号，并在每本书上贴上其编号。这 $n$ 本书中的每一本都应被赋予一个从 $1$ 到 $n$ 的编号。显然，不同的书必须被赋予不同的编号。

万尼亚想知道，在为所有图书编号时，他总共需要写下多少个数字。

The first line contains integer n (1 ≤ n ≤ 109) — the number of books in the library.

第一行包含一个整数 $n$（$1 \leq n \leq 10^9$）—— 图书馆中书籍的数量。

Print the number of digits needed to number all the books.

输出为所有图书编号所需的数字位数。

Note to the first test. The books get numbers 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, which totals to 17 digits.

Note to the second sample. The books get numbers 1, 2, 3, 4, which totals to 4 digits.

第一个测试用例说明：书籍编号为 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13，共包含 17 位数字。

第二个样例说明：书籍编号为 1, 2, 3, 4，共包含 4 位数字。