#include <bits/stdc++.h>
#include <chrono>
using namespace std;
#define reps(i,s,n) for(int i = s; i < n; i++)
#define rep(i,n) reps(i,0,n)
#define Rreps(i,n,e) for(int i = n - 1; i >= e; --i)
#define Rrep(i,n) Rreps(i,n,0)
#define ALL(a) a.begin(), a.end()
#define fi first
#define se second
typedef long long ll;
typedef vector<ll> vec;
typedef vector<vec> mat;

ll N,M,H,W,Q,K,A,B;
string S;
typedef pair<ll, ll> P;
const ll INF = (1LL<<58);


int main() {
    cin>>N;
    ll ans = 0;
    reps(i, 10, min(100LL, N + 1)){
        if(i%3 == 0 && ((i%10) + (i/10))%3 == 0) ++ans;
    }
    queue<ll> que;
    que.push(3); que.push(6); que.push(9);
    while(!que.empty()){
        ll q = que.front(); que.pop();
        if(q >= 100) ++ans;
        for(int i : {0, 3, 6, 9}){
            ll temp = q * 10 + i;
            if(temp <= N) que.push(temp);
        }
    }
    cout<<ans<<endl;
}