#include<iostream>
#include<string.h>
#include<algorithm>
#include<vector>
#include<math.h>
using namespace std;

int main()
{
    long long a,b,n,count=1,sum;
    cin>>a>>b>>n;
    sum=a;
    while(sum<n)
    {
        if(count%7==0 || (count+1)%7==0)
            sum+=b;
        else
            sum+=a;
        count++;
    }
    cout<<count;
	return 0;
}