#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
LL a,b,n;
int main(){
scanf("%lld%lld%lld",&a,&b,&n);
LL week =5*a+2*b;
LL weeks =n/week;
LL tleft = n%week;
if(tleft==0){printf("%lld",weeks*7);return 0;}
for(int i=1;i<=5;i++){
if(tleft<=i*a){printf("%lld",weeks*7+i);return 0;}
}
for(int i=1;i<=2;i++){
if(tleft<=5*a+i*b){printf("%lld",weeks*7+5+i);return 0;}
}
}