https://codeforces.com/contest/552/problem/B

#include <bits/stdc++.h>
using namespace std;
int a[1005];
int l;
typedef long long ll;
int main()
{
    int n;
    cin >> n;
    ll t = 1;
    ll res = 0;
    while (n-t>=0){
        res += n - t + 1;   //每位出现的数字个数
        t *= 10;
    } 
    cout << res << endl;
    return 0;
}