#include<bits/stdc++.h>
using namespace std;
int main(){
    long long a,b,n,sum=0,day=1,m,k=0;
    cin>>a>>b>>n;
    m=5*a+2*b;
    k=n/m;
    day+=k*7;
    n=n-m*k;
    while(sum<n){
    	if(day%6==0||day%7==0){
    		sum+=b;
		}else{
			sum+=a;
		}
		day++;
	}
	cout<<day-1;
    return 0;c
}