#include <bits/stdc++.h>
using namespace std;
using ll = long long;
template <class T> using vec = vector<T>;
template <class T> using vvec = vector<vec<T>>;
template <class T> using vvvec = vector<vvec<T>>;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N;
    cin >> N;
    int ans = 0;
    for(int i=10;i<=min(N,99);i++){
        if(i%3==0){
            int c = i/10%3+i%10;
            if(c%3==0) ans++;
        }
    }
    if(N<100){
        cout << ans << "\n";
        return 0;
    }

    set<int> s;
    auto dfs = [&](auto&& self,ll n)->void{
        if(n%3==0 && n>=100) s.insert(n);
        for(auto& x:{0,3,6,9}){
            if(10*n+x<=N) self(self,10*n+x);
        }
    };
    for(auto& x:{3,6,9}) dfs(dfs,x);
    ans += s.size();
    cout << ans << "\n";
}