#include<bits/stdc++.h>
using namespace std;
#define int long long
signed main()
{
	int a,b,c,d;cin>>a>>b>>c>>d;
	int n;cin>>n;
	int mn=1e10;mn=min({mn,a*8,b*4,c*2,d});
	int ans=0;
	ans+=mn*(n>>1);
	n=n%2;
	if(n==1)ans+=min({a*4,b*2,c});
	cout<<ans;
	return 0;
}

#include<bits/stdc++.h>
using namespace std;
#define int long long
signed main()
{
	int a,b,c,d;cin>>a>>b>>c>>d;
	int n;cin>>n;
	int mn=1e10;mn=min({mn,a*8,b*4,c*2,d});
	int ans=0;
	ans+=mn*(n>>1);
	n=n%2;
	if(n==1)ans+=min({a*4,b*2,c});
	cout<<ans;
	return 0;
}