#include<iostream>

using namespace std;

int main(){
//int W,H,x,y,r;
    int a,b,c;
    int i=0;
    cin>>a>>b>>c;
int ans=0;
while(ans<c){
i++;
ans+=a;
if(i%7==0)
ans+=b;
}
   cout<<i<<endl;   
  
  
  return 0;
}
