Problem:
Score : 300 points

Problem Statement

You've come to your favorite store Infinitesco to buy some ice tea.

The store sells ice tea in bottles of different volumes at different costs.
Specifically, a 0.25-liter bottle costs Q yen, a 0.5-liter bottle costs H yen, a 1-liter bottle costs S yen, and a 2-liter bottle costs D yen.
The store has an infinite supply of bottles of each type.

You want to buy exactly N liters of ice tea. How many yen do you have to spend?

Constraints

1 \leq Q, H, S, D \leq 10^8

1 \leq N \leq 10^9

All input values are integers.

Input

Input is given from Standard Input in the following format:

Q H S D
N

Output

Print the smallest number of yen you have to spend to buy exactly N liters of ice tea.

Sample Input 1

20 30 70 90
3

Sample Output 1

150

Buy one 2-liter bottle and two 0.5-liter bottles. You'll get 3 liters for 90 + 30 + 30 = 150 yen.

Sample Input 2

10000 1000 100 10
1

Sample Output 2

100

Even though a 2-liter bottle costs just 10 yen, you need only 1 liter.
Thus, you have to buy a 1-liter bottle for 100 yen.

Sample Input 3

10 100 1000 10000
1

Sample Output 3

40

Now it's better to buy four 0.25-liter bottles for 10 + 10 + 10 + 10 = 40 yen.

Sample Input 4

12345678 87654321 12345678 87654321
123456789

Sample Output 4

1524157763907942

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using static System.Console;

class Program {
    static void Main() {
        var q = NextInt();
        var h = NextInt();
        var s = NextInt();
        var d = NextInt();
        var n = (long)NextInt();

        foreach (var v in new int[] { 4 * q, 2 * h }) {
            s = Math.Min(s, v);
        }
        WriteLine(s * (n % 2) + Math.Min(2 * s, d) * (n / 2));
    }

    static int NextInt() {
        return int.Parse(NextString());
    }

    static string NextString() {
        var result = new List<char>();
        while (true) {
            int next = Read();
            if (next < 0)
                break;
            var nextChar = (char)next;
            if (!char.IsWhiteSpace(nextChar))
                result.Add(nextChar);
            else if (nextChar != '\r')
                break;
        }
        return string.Join("", result);
    }
}