#include <bits/stdc++.h>
using namespace std;
using ll=long long;
int main()
{
    string a;
    cin>>a;
    int n=a.size();
    ll ans=0;
    ll cnt0=0;
    for (char x:a) if (x=='0') cnt0++;
    if (cnt0==n-1 && a[0]!='1'){
        ans++;
        string b;
        b+=to_string(a[0]-'1');
        for (int i=1; i<n;i++) b+='9';
        a=b;

    }
    for (char x:a){
        ans+=x-'0';
    }
    for (int i=n-1; i>0; i--) ans+=9*i;
    cout<<ans;

}