/**
*   auther:  deviceF
*   created: 19.04.2024 21:11:10
**/
#include<bits/stdc++.h>

using namespace std;

int main(){
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  string s = to_string(n);
  int size = (int)s.size();
  cout << 9 * size + 9 << '\n';
  return 0;
}