#include <bits/stdc++.h>
using namespace std;
 
int main() {
  long n,ans;
  cin >> n;
  ans=n/11*2;
  n=n%11;
  if(n>0) ans++;
  if(n>6) ans++;
  cout << ans << endl;
}
#include <iostream>

int main()
{
    std::string s; std::cin >> s;

    for (size_t i = 0; i < s.size() - 8; i++) {
        std::cout << s[i];
    }
    std::cout << std::endl;
    return 0;
}
