#include <bits/stdc++.h>

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  string S;
  cin >> S;
  int N = S.size();
  vector<vector<int>> dp(N + 1, vector<int>(2, 0));
  dp[0][0] = 1;
  for (int i = 0; i < N; i++) {
    int c = S[i] - '0';
    for (int j = 0; j < 10; j++) {
      for (int k = 0; k < 2; k++) {
        if (k == 0 && j > c) continue;
        if (j % 3 != 0) continue;
        int nk = j < c ? 1 : k;
        dp[i + 1][nk] += dp[i][k];
      }
    }
  }
  int res = dp[N][0] + dp[N][1] - 4;
  for (int i = 10; i < min(100, stoi(S) + 1); i++) {
    int x = i;
    while (x > 0 && x % 3 == 0) {
      x /= 10;
    }
    if (x != 0 && i % 3 == 0) res++;
  }
  cout << res << '\n';
  return 0;
}