import java.util.Scanner;

public class Main{
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        int a=sc.nextInt();
        int b=sc.nextInt();
        int n=sc.nextInt();
        int t=1;
        int m=0;

        while(m<n)
        {
            if(t%7<=5)
            m=(t/7)*(5*a+2*b)+(t%7)*a;
        else
            m=(t/7)*(5*a+2*b)+((t%7)-5)*b+5*a;
            t++;
        }
        System.out.println(t-1);
    }
}