#include <iostream>
#include <string>
using namespace std;
typedef long long ll;

int main() {
    ll n;
    cin >> n;
    ll num = 1e9 + 1;
    if(n < num) {
        cout << 0 << endl;
        return 0;
    } else {
        ll a = n / num;
        ll ans = 0;
        int ma = 9;
        while(a > 0) {
            ma = min<ll>(ma, a%10);
            a /= 10;
            ans += 9;
        }
        ans -= 9;
        ans += ma;
        cout << ans << endl;
    }


}