#include <iostream>
#include <math.h>
#define ll long long
using namespace std;

void solve() {

  int n; cin >> n;
  cout << ceil((float)n / 3) << endl;
  
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(nullptr);
    int t = 1; 
    //cin >> t;  
    for (int i = 1; i <= t; i++) {
        solve();  
    }
    return 0;
}