unsigned long long a,b,k,d,x;
    cin>>a>>b>>k>>d>>x;
    unsigned long long  l=0, r=1e20;
    while(r-l!=1){
        unsigned long long m = (l+r)/2;
        if ((m*(a+b)- a*(m/k) - b*(m/d))<x){
            l=m;
        }
        else
            r=m;
    }
    cout<<r;
    return 0;
}