#include<stdio.h>

int main(){
	long long a,b,n;
	int days=0,num=0,week=0;
	
	scanf("%ld%ld%ld",&a,&b,&n);
	
	week=n/(a*5+b*2);
	n=n%(a*5+b*2);
	while(num<n){
		days++;
		if(days%7<=5&&days%7>=1){
			num=num+a;
		}
		if(days%7==6||days%7==0){
			num=num+b;
		}	
	}
	days=days+week*7;
	
	printf("%d",days);
	
	return 0;
}