#include <bits/stdc++.h>
#define rep(i,n) for (int i = 0; i < (int)(n); i ++)
#define irep(i,n) for (int i = (int)(n) - 1;i >= 0;--i)
using namespace std;
using ll = long long;
using PL = pair<ll,ll>;
using P = pair<int,int>;
constexpr int INF = 1000000000;
constexpr long long HINF = 1000000000000000;
constexpr long long MOD = 1000000007;// = 998244353;
constexpr double EPS = 1e-4;
constexpr double PI = 3.14159265358979;

ll N;
int ans = 0;
void dfs(ll v) {
    if (v >= 10 && v%3 == 0 && v <= N) ++ans;
    if (10*v > N) return;
    dfs(v*10); dfs(v*10 + 3); dfs(v*10 + 6); dfs(v*10 + 9);
    return;
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    cin >> N;
    dfs(3LL); dfs(6LL); dfs(9LL);
    rep(i,10)rep(j,10) {
        if ((i + j)%3 == 0 && (i%3 != 0) && 10*i + j <= N) ++ans;
    }
    cout << ans <<'\n';
    return 0;
}