#include <bits/stdc++.h>
using namespace std;
int main(void){
    int a,b,c,sum=0,count=0,login=0;
    cin>>a>>b>>c;
    while (sum<c) {
        login++;
        count++;
        sum+=a;
        if (count==7) {
            sum+=b;
            count=0;
        }
    }
    cout<<login<<endl;
}
