#include <bits/stdc++.h>
#define int long long
#define sqrt(x) sqrtl(x)
using namespace std;

namespace solve {
  namespace test_case {
    void main() {
      int n; cin >> n;
      cout << n / 3 +  (n % 3 > 0) << '\n';
    }
  }

  void main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int t (1); //cin >> t; 
    while (t--) {
      test_case::main();
    }
  }
}

signed main() { solve::main(); }