#include <iostream>
#include <vector>
#include <map>
#include <queue>
#include <string>
#include <set>
#include <algorithm>
#include <list>
using namespace std;
using ll = long long int;

int main(){
    string s;
    cin >> s;
    int answ = 0;
    if(s.size() > 1){
        while(s.size() > 1){
            //cerr << s << endl;
            sort(s.begin(), s.end());
            int i = lower_bound(s.begin(), s.end(), '1') - s.begin();
            swap(s[0],s[i]);
            i = s.size() - 1;
            if(s[i] == '0'){
                s = s.substr(0,1) + string(s.size() - 1, '9');
                --s[0];
            }
            else{
                --s[i];
            }
            while(*s.begin() == '0'){
                s.erase(s.begin());
            }
            ++answ;
        }
        answ += atoi(s.c_str());
        cout << answ << endl;
    }
    else{
        cout << atoi(s.c_str()) << endl;
    }
    return 0;
}