#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (ll i = 0; i < (n); ++i)
#define rep1(i, n) for (ll i = 1; i < (n); ++i)
#define rrep(i, n) for (ll i = n; i > 0; --i)
#define bitrep(i, n) for (ll i = 0; i < (1 << n); ++i)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define yesNo(b) ((b) ? "Yes" : "No")
using ll = long long;
using ull = unsigned long long;
using ld = long double;
string alphabet = "abcdefghijklmnopqrstuvwxyz";
string ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
const double pi = 3.141592653589793;
int smallMOD = 998244353;
int bigMOD = 1000000007;

int main()
{
    ll x;
    cin >> x;
    if (x < 1e9)
    {
        cout << 0 << endl;
    }
    else if (x < 1e10)
    {
        int ans = x / 1e9;
        if (x % 1000000000ll < ans)
        {
            ans--;
        }
        cout << ans << endl;
    }
    else if (x < 1e11)
    {
        int ans = 9 + x / 1e10;
        if (x % 10000000000ll < ans)
        {
            ans--;
        }
        cout << ans << endl;
    }
    else if (x < 1e12)
    {
        int ans = 18 + x / 1e11;
        if (x % 100000000000ll < ans)
        {
            ans--;
        }
        cout << ans << endl;
    }
    else if (x < 1e13)
    {
        int ans = 27 + x / 1e12;
        if (x % 1000000000000ll < ans)
        {
            ans--;
        }
        cout << ans << endl;
    }
    else if (x < 1e14)
    {
        int ans = 36 + x / 1e13;
        if (x % 10000000000000ll < ans)
        {
            ans--;
        }
        cout << ans << endl;
    }
    else if (x < 1e15)
    {
        int ans = 45 + x / 1e14;
        if (x % 100000000000000ll < ans)
        {
            ans--;
        }
        cout << ans << endl;
    }
    else if (x < 1e16)
    {
        int ans = 54 + x / 1e15;
        if (x % 1000000000000000ll < ans)
        {
            ans--;
        }
        cout << ans << endl;
    }
    else if (x < 1e17)
    {
        int ans = 63 + x / 1e16;
        if (x % 10000000000000000ll < ans)
        {
            ans--;
        }
        cout << ans << endl;
    }
    else if (x < 1e18)
    {
        int ans = 72 + x / 1e17;
        if (x % 100000000000000000ll < ans)
        {
            ans--;
        }
        cout << ans << endl;
    }
    else if (x < 1e19)
    {
        int ans = 81 + x / 1e18;
        if (x % 1000000000000000000ll < ans)
        {
            ans--;
        }
        cout << ans << endl;
    }
    return 0;
}