#include <iostream>

#define DAY 7 

using namespace std;

int main(void)
{
  int A, B, C;
  cin >> A >> B >> C;

  int coin = 0;
  int i = 0;
  while(coin < C) {
    i++;
    coin += A;
    if(i % DAY == 0) coin += B;
  }

  cout << i << endl;

  return 0;
}
