// lanqiao 2098 刷题统计(数学优化)
#include<bits/stdc++.h>
using namespace std;
#define int long long
signed main(){
    int a, b, n; cin >> a >> b >> n;
    int d = 5 * a + 2 * b;
    if(n % d == 0) cout << (n/d)*7 << endl;
    else{
        int r = n % d, sum = 0;
        for(int i = 1; i <= 7; i++){
            if(i <= 5) sum += a;
            else sum += b;
            if(sum >= r){
                cout << (n/d)*7 + i << endl;
                return 0;
            }
        }
    }
    return 0;
}
/* test samples -> 8
10 20 99
*/