#include<iostream>
using namespace std;

int main(){
  int a,b,c;
  int coin=0,day=0;
  cin>>a>>b>>c;

  do{
    day++;
    coin += a;
    if(day%7 == 0){
      coin += b;
    }
  }while(coin < c);
  cout<<day<<endl;

  return 0;
}
