#include <iostream>
using namespace std;
int a, s = 9, dem = 0, so = 1;
int main() 
{
    cin >> a;
    for(int b = 1; b <= a + 1; b++)
    {
        if(b <= s) dem += so;
        else if(b > s)
        {
            s = s*10 + 9;
            so++;
        }
    }
    cout << dem;
    return 0;
}

$#khanhtaon$