import java.util.*;
public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		long a = sc.nextLong();
		long b = sc.nextLong();
		long n = sc.nextLong();
		
		long week = n / (5*a+2*b);
		
		n = n % (5*a+2*b);
		
		
		long day = 0;
		while(n>0) {
			if(day<6) {
				n -= a;
				day++;
			}else {
				n -= b;
				day++;
			}
		}
		System.out.println(day+week*7);
	}
}