#include <iostream>
using namespace std;
int main(void){
    int a,b,c,sum=0,n;
    cin >> a >> b >>c;
    //if(c/a > 7){
        for(int i=0; i<100000000; i++){
            sum=i*a+i/7*b;
            if(c<=sum){
                cout << i << endl;
                break;
            }
        }
    //}
    //else{
        //n=c/a;
        //cout << n << endl;
    //}
}

