#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
signed main() {
  ios::sync_with_stdio(false); cin.tie(0);
  int a, b, c;
  cin >> a >> b >> c;
  int coins = 0;
  int ans = 0;
  while (true) {
    if (coins >= c) {
      cout << ans << endl;
      return 0;
    }
    coins += a;
    ans++;
    if (ans % 7 == 0) coins += b;
  }
  return 0;
}
