#include <iostream>
using namespace std;
int main(void){
    int a,b,c,sum=0,day=0,i;
    cin>>a>>b>>c;
    while(sum<c){
        sum+=a;
        day++;
        i++;
        if(i==7){
            i=0;
            sum+=b;
        }
    }
    cout<<day<<endl;
}

