#include <iostream>

int main(){
	long a, b, c, i = 1, total = 0;
	std::cin >> a >> b >> c;
	while (total < c) {
		total += a;
		if (i != 0 && ((i % 7) == 0)) total += b;
		i++;
	}

	std::cout << i - 1 << std::endl;
	return 0;
}
