#include<bits/stdc++.h>
using namespace std;
int a,b,n,day=0,ti=0;
int main(){
	cin>>a>>b>>n;
	while(ti<=n){
		if(day%7==6||day%7==0){
			ti+=b;
		}else{
			ti+=a;
		}
		day++;	
	}
	cout<<day;
	return 0;
}