#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define all(v) begin(v), end(v)
#define FOR(i,a,b) for(int i=(a);i<(int)(b);i++)
#define rep(i,b) FOR(i,0,b)

const ll mod = 1e9+7;
ll INF = 1000;

ll n,k,a[100010],b[100010],ans;
string s;
int main(){
  cin>>n;
  s=to_string(n);
  //cout<<s<<endl;
  int top=s[0]-'0';
  int bottom=s[s.size()-1]-'0';
  int keta=s.size();
  if(s.size()<9){
    cout<<0<<endl;
    return 0;
  }

  keta-=9;
  rep(i,keta-1)ans+=9;

  if(top>1)ans+=top-1;
  else{
    if(n>1000000001)ans++;
  }

  cout<<ans<<endl;
  return 0;
}