#include <iostream>
#include <vector>
#include <deque>
#include <math.h>
#include <set>
#include <iomanip>
#include <time.h>
#include <list>
#include <stdio.h>
#include <queue>
#include <map>
#include <algorithm>
#include <assert.h>
#include <memory.h>

#define mk make_pair
#define sc second
#define fr first
#define pb emplace_back
#define all(s) s.begin(), s.end()
#define sz(s) ( (int)s.size() )
#define int long long

using namespace std;

int a, b, c, d, n;

main ()
{
    cin >> a >> b >> c >> d >> n;
    b = min(a + a, b);
    c = min(b + b, c);
    d = min(c + c, d);
    if (n & 1)
        cout << n / 2 * d + c << endl;
    else
        cout << n / 2 * d << endl;
}
