// package agc.agc019;

import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.InputMismatchException;

public class Main {
    public static void main(String[] args) {
        InputReader in = new InputReader(System.in);
        PrintWriter out = new PrintWriter(System.out);

        long q = in.nextLong();
        long h = in.nextLong();
        long s = in.nextLong();
        long d = in.nextLong();
        long n = in.nextLong() * 4;

        long[] eight = new long[]{q*8, h*4, s*2, d};
        Arrays.sort(eight);

        long ei = n / 8;
        long best8 = eight[0];
        long score = best8 * ei + dfs(q, h, s, d, n % 8);

        out.println(score);
        out.flush();
    }

    private static long dfs(long q, long h, long s, long d, long left) {
        if (left == 0) {
            return 0;
        }
        long best = Long.MAX_VALUE;
        if (left >= 1) {
            best = Math.min(best, dfs(q, h, s, d, left-1) + q);
        }
        if (left >= 2) {
            best = Math.min(best, dfs(q, h, s, d, left-2) + h);
        }
        if (left >= 4) {
            best = Math.min(best, dfs(q, h, s, d, left-4) + s);
        }
        return best;
    }

    public static class InputReader {
        private static final int BUFFER_LENGTH = 1<<12;
        private InputStream stream;
        private byte[] buf = new byte[BUFFER_LENGTH];
        private int curChar;
        private int numChars;

        public InputReader(InputStream stream) {
            this.stream = stream;
        }

        private int next() {
            if (numChars == -1) {
                throw new InputMismatchException();
            }
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0)
                    return -1;
            }
            return buf[curChar++];
        }

        public char nextChar() {
            return (char)skipWhileSpace();
        }

        public String nextToken() {
            int c = skipWhileSpace();
            StringBuilder res = new StringBuilder();
            do {
                res.append((char) c);
                c = next();
            } while (!isSpaceChar(c));
            return res.toString();
        }

        public int nextInt() {
            return (int)nextLong();
        }

        public long nextLong() {
            int c = skipWhileSpace();
            long sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = next();
            }
            long res = 0;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = next();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public double nextDouble() {
            return Double.valueOf(nextToken());
        }

        int skipWhileSpace() {
            int c = next();
            while (isSpaceChar(c)) {
                c = next();
            }
            return c;
        }

        boolean isSpaceChar(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }
    }
}


Measured memory_bytes: 21076