#include<iostream>
using namespace std;
typedef long long LL;
LL a,b,n,res;
int main()
{
    cin>>a>>b>>n;
    LL week;
    week=n/(5*a+2*b);
    res=7*week;
    n-=week*(5*a+2*b);
    for(int i=1;i<=5;i++) 
    if(n>0)
    {
        n-=a;res++;
    }
    for(int i=1;i<=2;i++)
    if(n>0)
    {
        n-=b;res++;
    }
    cout<<res<<endl;
}