#include <bits/stdc++.h>
using namespace std;

int main() {
  int N;
  cin >> N;
  int ans = 0;
  auto dfs = [&](auto &&dfs, long n) -> void {
    if (n > N) return;
    if (n > 9) ans++;
    string s = to_string(n);
    for (int next = 0; next <= 9; next++) {
      for (int i = 0; i < s.size(); i++) {
        int tmp = s.at(i) - '0';
        if ((tmp + next) % 3) goto NG;
      }
      dfs(dfs, n * 10 + next);
      NG:;
    }
  };
  for (int i = 1; i <= 9; i++) dfs(dfs, i);
  cout << ans << "\n";
}