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: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace AGC019A {
    class Program {
        static void Main(string[] args) {
            int[] input = Console.ReadLine().Split(' ').Select(s => int.Parse(s)).ToArray();
            int Q = input[0];
            int H = input[1];
            int S = input[2];
            int D = input[3];
            long N = int.Parse(Console.ReadLine());
            bool[] flags = Enumerable.Repeat(true, 4).ToArray();
            if (Q * 2 < H) {
                flags[1] = false;
            }
            if (H * 2 < S) {
                flags[2] = false;
            }
            if (S * 2 < D) {
                flags[3] = false;
            }
            long ans = 0;
            long num = N / 2;
            if (flags[3]) {
                ans += num * D;
                N -= num * 2;
            }
            if (flags[2]) {
                ans += N * S;
                N = 0;
            }
            if (flags[1]) {
                ans += N * 2 * H;
                N = 0;
            }
            ans += N * 4 * Q;
            N = 0;
            Console.WriteLine(ans);
        }
    }
}