#include<bits/stdc++.h>
using namespace std;
long long a,b,n,day=1,ans=0,sum=0;
int main() 
{
    scanf("%lld%lld%lld",&a,&b,&n);
    for(int sum<n) 
    {
        (day>=6)?sum+=b:sum+=a;
        day=day%7+1;
        ++ans;
    } 
    printf("%lld",ans);
    return 0;
}

//AC必关QwQ