#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define all(x) (x).begin(),(x).end()

typedef long long ll;
typedef pair<ll, ll> P;

const int mod =  1000000007;  //出力は (ans % mod + mod) % mod  (負の剰余を正にする)
const int inf = 1e9;
const long long INF = 1LL << 60;   // INF = 11

ll l[4] = {0,3,6,9};
ll ans = 0;
 
void dfs(ll tmp,ll lim){
    //cout << tmp << endl;
    if(tmp <= lim){
        if(tmp >= 100) ans++;
        for(int i = 0; i < 4; i++){
            dfs(tmp * 10 + l[i],lim);
        }
    }

}

int main()
{
    ll n; cin >> n;
    if(n <= 100){
        cout << n/3 - 3 << endl;
    }else{
        dfs(3,n);
        dfs(6,n);
        dfs(9,n);
        cout << 30 + ans << endl;
    }

}