#include <bits/stdc++.h>
using namespace std;
int main(){
  int N;
  cin >> N;
  int tv = 14000, fv = 0;
  while (tv - fv > 1){
    int mid = (tv + fv) / 2;
    if (N + mid / 7 * 6 <= mid){
      tv = mid;
    } else {
      fv = mid;
    }
  }
  cout << tv << endl;
}