#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i = 0; i < (n);i++)
#define sz(x) int(x.size())
typedef long long ll;
typedef long double ld;
typedef pair<int,int> P;

int main() {
  int m;
  cin >> m;
  string s;
  s = to_string(m);
  int n = s.size();
  int res = 0;
  string cur = "";
  auto dfs = [&](auto& f, int len)->void{
    if (len > n) return ;
    int t = 0;
    int ok = 1;
    for (int i = 0; i < len; i++) {
      int a = cur[i] - '0';
      t = t * 10 + a;
      for (int j = i + 1; j < len; j++) {
        int b = cur[j] - '0';
        if ((a + b) % 3 != 0) ok = 0;
      }
    }
    if (len > 1) ok &= (t % 3 == 0);
    if (t <= m && len > 1) {
      res += ok;
    }
    if (!ok) return ;
    for (int d = (len ? 0 : 1); d <= 9; d++) {
      cur += char(d + '0');
      f(f, len + 1);
      cur.pop_back();
    }
  };

  dfs(dfs, 0);

  cout << res << endl;
  return 0;
}