#include<iostream>
using namespace std;
int main(){

	int A, B, C;
	int have = 0, ans = 0;
	cin >> A >> B >> C;
	for (int i = 1; i <= C; i++){
		have += A;
		if (i % 7 == 0) have += B;
		if (have >= C){
			ans = i;
			break;
		}
	}

	cout << ans << endl;

	return 0;
}
