#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  cin.tie(nullptr)->sync_with_stdio(false);
  int n;
  cin >> n;
  set<int> s;
  function<void(ll)> dfs = [&](ll x) {
    if (x > n) return;
    if (x >= 100) s.insert(x);
    if (x != 0) dfs(x * 10 + 0);
    dfs(x * 10 + 3);
    dfs(x * 10 + 6);
    dfs(x * 10 + 9);
  };
  dfs(0);
  for (int x = 10; x <= min(n, 99); ++x) {
    if (((x / 10) + (x % 10)) % 3 == 0) s.insert(x);
  }
  //Debug(s);
  cout << s.size() << '\n';
  return 0;
}