#include <cstdlib>
#include <iostream>

using namespace std;

int main(){
    int day = 0;
    int coin = 0;
    int a,b,c;
    cin >> a >> b >> c;


    while(coin < c){
        day ++;
        coin += a;
        if(day % 7 == 0){
            coin += b;
        }
    }

    cout << day << endl;

    return 0;
}
