#include <iostream>
using namespace std;

int main(){
  long q,h,s,d,n;
  cin >> q >> h >> s >> d >> n;
  if(n%2==0){
    cout << min(min(min(8*q, 4*h),2*s), d)*(n/2);
  }else{
    cout << min(min(4*q,2*h),s)+min(min(min(8*q, 4*h),2*s), d)*(n/2);
  }
}