#include <bits/stdc++.h>

using namespace std;
using lint = long long;

lint n;
int ans = 0;

void dfs(lint cur) {
    if (cur > n) return;
    if (cur > 100) ans++;

    dfs(cur * 10);
    dfs(cur * 10 + 3);
    dfs(cur * 10 + 6);
    dfs(cur * 10 + 9);
}

int main() {
    cin >> n;

    // 2桁の場合
    for (lint i = 12; i < 100 and i <= n; i += 3) {
        ans++;
    }

    // 3桁以上の場合
    dfs(3);
    dfs(6);
    dfs(9);

    cout << ans << endl;
    return 0;
}