// lanqiao 2098 刷题统计(枚举法)
#include<bits/stdc++.h>
using namespace std;
#define int long long
signed main(){
    int a, b, n; cin >> a >> b >> n;
    int sum = 0, i;
    for(i = 1; ;i++){
        if(i % 7 != 0 && i % 7 != 6){
            sum += a;
        }else{
            sum += b;
        }
        if(sum >= n) break;
    }
    cout << i << endl;
    return 0;
}
/* test samples -> 8
10 20 99
*/