import java.util.Scanner;
public class Test5 {
	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/(a*5+b*2);
		long temp=n%(a*5+b*2);
		long sday=0;
		long sum=0;
		while(true) {
			sday++;
			if(sday%7<=5&&sday%7!=0){
				sum+=a;
			}else {
				sum+=b;
			}
			if(sum>temp) {
				break;
			}
		}
        System.out.print(7*week+sday);     
        sc.close();
    }
}