#include<bits/stdc++.h>
using namespace std;
unsigned long long a,b,n,tishu,sum;
int main(){
	cin>>a>>b>>n;
	for(int i=1;;i++){
		if(i%7==0||i%6==0){
			tishu+=b;
		}
		else{
			tishu+=a;
		}
		sum++;
		if(tishu>=n){
			cout<<sum;
			return 0;
		}
	}
	return 0;
}