#include<iostream>
using namespace std;

int main(void){
    int a,b,c,day = 0,sum = 0;

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

    cout << day << endl;
}
