B. Vanya and Books

time limit per test
1 second

memory limit per test
256 megabytes

input
standard input

output
standard output

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.

Input

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

Output

Print the number of digits needed to number all the books.
Examples
input
13
output
17
input
4
output
4
Note

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.

题意：

求从1~n共出现了多少个数字。

附AC代码：

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 
 4 int main(){
 5     int n;
 6     cin>>n;
 7     long long  ans=1,sum=0;
 8     while(n-ans>=0){
 9         sum+=n-ans+1;
10         ans*=10;
11     }
12     cout<<sum<<endl;
13     return 0;
14 }