#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <iomanip>
#include <stack>
#include <algorithm>
#include <string>
#include <map>
#include <iterator>
#include <set>
#include <queue>
#include <bitset>
#include <cassert>

using namespace std;

vector<int> ps = {0, 3, 6, 9};

int m(int x, int k) {
    if (x > k) {
        return 0;
    }
    
    int cnt = 1;
    for (int i = 0; i < 4; ++i) {
        cnt += m(x * 10 + ps[i], k);
    }
    return cnt;
}

int main() {

    vector<int> xs;
    for (int i = 10; i < 100; ++i) {
        if (i % 3 == 0 and ((i / 10) + (i % 10)) % 3 == 0) {
            xs.push_back(i);
        }
    }

    int N;
    cin >> N;

    if (N < 100) {
        int cnt = 0;
        for (int i = 0; i < xs.size(); ++i) {
            if (xs[i] <= N) {
                cnt += 1;
            }
        }
        cout << cnt << endl;
    } else {

        int cnt = xs.size();
        vector<int> ys;
        for (int i = 0; i < xs.size(); ++i) {
            if ((xs[i] % 10) % 3 == 0 and (xs[i] / 10) % 3 == 0) {
                ys.push_back(xs[i]);
            }
        }
        cnt -= ys.size();
        for (int i = 0; i < ys.size(); ++i) {
            cnt += m(ys[i], N);
        }

        cout << cnt << endl;
    }

}