#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll=long long;
using ld=long double;
ld pie=3.141592653589793;
ll inf=144494;
ll mod=1000000007;
int main(){
    ll n;
    cin >>n;
    ll x=mod-6;
    ll ans=min(n/x,(ll)9);
    ll now=11;
    for (ll i = 0; i < 8; i++)
    {
        ans+=min(n/(x*now),(ll)9);
        now*=10;
        now+=1;
    }
    cout << ans << endl;
}