#include <iostream>
#include <vector>
#include <algorithm>

#define ll long long 
using namespace std;

ll n, i, j, a;

int main()
{
    ios::sync_with_stdio(false);
    cin >> n;
    a = n;
    ll db = 0;
    while (a > 0)
    {
        j += a % 10;
        db++;
        a /= 10;
    }

    cout << min(n,j + (((db - 1) * db) / 2) * 9);
}

// Run program: Ctrl + F5 or Debug > Start Without Debugging menu
// Debug program: F5 or Debug > Start Debugging menu

// Tips for Getting Started: 
//   1. Use the Solution Explorer window to add/manage files
//   2. Use the Team Explorer window to connect to source control
//   3. Use the Output window to see build output and other messages
//   4. Use the Error List window to view errors
//   5. Go to Project > Add New Item to create new code files, or Project > Add Existing Item to add existing code files to the project
//   6. In the future, to open this project again, go to File > Open > Project and select the .sln file