#include <iostream>
using namespace std;
int main(){
    int num,num2,num3,num4=0,i=0,j=0;
    cin >> num >> num2 >> num3;
    while(num4<num3){
        num4+=num;
        i++;
        if(i%7==0){
            num4+=num2;
            i=0;
        }
        j++;
    }
    cout << j << endl;
    return 0;
}
