50_vanya_and_books_codeforces.cpp

//
//  main.cpp
//  books
//
//  Created by Prince  Kumar on 15/08/19.
//  Copyright © 2019 Prince  Kumar. All rights reserved.
//    codeforce --> Vanya and Books

#include <iostream>
#include <math.h>
#define ll long long
using namespace std;
int main()
{
    ll int n; cin>>n;
    ll int a[13]={0};
    for(int i=1;i<13;i++)
    {
        a[i]=pow(10,i)-1;
    }
    for(int i=2;i<13;i++)
    {
        for(int j=1;j<=i-1;j++)
        {
            a[i] = a[i]-a[j];
        }
    }
//    for(int i=1;i<13;i++)
//    {
//        cout<<a[i]<<endl;
//    }
    // value in array is to set
    
    ll int count=0;
    for(int i=1;i<13;i++ )
    {
        if(n-a[i]>=0)
        {
            count+=a[i]*i;
            n=n-a[i];
        }
        else
        {
            count+=n*i;
            break;
        }
    }
    cout<<count<<endl;
    
}