//Q
#include<bits/stdc++.h>
using namespace std;
long long a,b,n,week,days,m;
int main()
{
cin>>a>>b>>n;
week=n/(5*a+2*b);
m=n%(5*a+2*b);
days+=week*7;
for(int i=1;i<=7;i++)
{
if(m<=0) break;
if(i<=5) m=m-a;
else m=m-b;
days++;
}
cout<<days<<endl;
return 0;
}