#include <bits/stdc++.h>
using namespace std;

using int32 = int32_t;
using int64 = int64_t;
int main(void ){
  int64 A, B, C;
  cin >> A >> B >> C;
  int64 res = 0, cnt = 0;
  while (C > 0) {
    cnt++;
    if (cnt > 0 && cnt % 7 == 0) {
      C -= B;
    }
    C -= A;
    res++;
  }
  cout << res << endl;
}
