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