#include <bits/stdc++.h>
using namespace std;
const long long INF = 10000000000000;
int main(){
  vector<long long> A;
  A.push_back(1);
  A.push_back(4);
  A.push_back(18);
  while (A.back() < INF){
    long long x = A.back();
    long long y = A[A.size() - 2];
    A.push_back(x * 8 - y * 17);
  }
  long long N;
  cin >> N;
  int M = 0;
  for (int i = 0; i < A.size(); i++){
    if (A[i] < N){
      M++;
    }
  }
  cout << N - M << endl;
}