/*
17D8101013F 森田　匡博
JOI0652.cpp 2019/10/31
ID:key4 使用言語:C++
*/

#include <iostream>
#include <cmath>

int main()
{
  int A, B;
  long long int C, sum, day;

  std::cin >> A >> B >> C;

  sum = 0, day = 1;
  while(sum < C) {
    sum += A;
    if(day % 7 == 0) {
      sum += B;
    }
    day++;
  }

  std::cout << day - 1 << "\n";
  return 0;
}

