#include <bits/stdc++.h>
using namespace std;
#define f(i,k,n) for(int i=k; i<n; i++)
#define ll long long
const int inf = INT_MAX;

void solve()
{
    string n;
    cin>>n;
    int l=n.length();
    int c=0;
    f(i,0,l)    c+=n[i]-'0';
    if(n[0]!='1' && c==n[0]-'0')   c+=(n[0]-'1')*9*(l-1);
    c+=(9*l*(l-1))>>1;
    cout<<c;
}

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    int t=1;
    //cin>>t;
    while(t--)  solve();
    return 0;
}