import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.BufferedWriter;
import java.io.Writer;
import java.io.OutputStreamWriter;
import java.util.InputMismatchException;
import java.io.IOException;
import java.util.NoSuchElementException;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author ogiekako
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        MyScanner in = new MyScanner(inputStream);
        MyPrintWriter out = new MyPrintWriter(outputStream);
        TaskA solver = new TaskA();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskA {
        long min(long... a) {
            long res = a[0];
            for (long b : a) res = Math.min(res, b);
            return res;
        }

        public void solve(int testNumber, MyScanner in, MyPrintWriter out) {
            long[] a = new long[4];
            for (int i = 0; i < 4; i++) {
                a[i] = in.nextInt();
            }
            long N = in.nextInt() * 4L;
            long res =
                    N / 8 * min(8 * a[0], 4 * a[1], 2 * a[2], 1 * a[3]) +
                            N % 8 / 4 * min(4 * a[0], 2 * a[1], 1 * a[2]) +
                            N % 4 / 2 * min(2 * a[0], 1 * a[1]) +
                            N % 2 / 1 * min(1 * a[0]);
            out.println(res);
        }

    }

    static class MyPrintWriter {
        PrintWriter out;

        public MyPrintWriter(OutputStream outputStream) {
            out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        }

        public MyPrintWriter(Writer writer) {
            out = new PrintWriter(writer);
        }

        public void println(Object... os) {
            if (os.length == 0) {
                out.println();
                return;
            }
            for (int i = 0; i < os.length - 1; i++) {
                out.print(os[i]);
                out.print(' ');
            }
            out.println(os[os.length - 1]);
        }

        public void close() {
            out.close();
        }

    }

    static class MyScanner {
        private final InputStream in;
        private static final int BUFSIZE = 65536;
        int bufLen;
        int bufPtr;
        byte[] buf = new byte[BUFSIZE];

        public MyScanner(InputStream in) {
            this.in = in;
        }

        public int read() {
            if (bufLen == -1)
                throw new InputMismatchException();
            if (bufPtr >= bufLen) {
                bufPtr = 0;
                try {
                    bufLen = in.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (bufLen <= 0)
                    return -1;
            }
            return buf[bufPtr++];
        }

        public int nextInt() {
            int c = read();
            if (c == -1) throw new NoSuchElementException();
            while (c != '-' && (c < '0' || '9' < c)) {
                c = read();
                if (c == -1) throw new NoSuchElementException();
            }
            if (c == '-') return -nextInt();
            int res = 0;
            do {
                res *= 10;
                res += c - '0';
                c = read();
            } while ('0' <= c && c <= '9');
            return res;
        }

    }
}



Measured memory_bytes: 23380