#include<bits/stdc++.h>
using namespace std;
int main()
{
	long long sum=0,a,b,c,day=0;
	cin>>a>>b>>c;
	while(sum<c)
	{
		day++;
		if(day%6==0 or day%7==0)
		{
			sum+=b;
		}
		else
		{
			sum+=a;
		}
	}
	cout<<day;
	return 0;
}