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 System.Linq;
using System.Numerics;

    class Program
    {
        static void Main(string[] args)
        {
            var plain = Console.ReadLine().Split(' ').Select(s => int.Parse(s)).ToArray();
            var N = double.Parse(Console.ReadLine());
            var input = new List<KeyValuePair<int, double>>();
            input.Add(new KeyValuePair<int, double>(plain[0],0.25));
            input.Add(new KeyValuePair<int, double>(plain[1],0.5));
            input.Add(new KeyValuePair<int, double>(plain[2],1));
            input.Add(new KeyValuePair<int, double>(plain[3],2));
            input = input.OrderBy(cost => cost.Key * (2 / cost.Value)).ToList();
            var suml = 0.0;
            BigInteger sumMoney = 0;
            foreach(var item in input)
            {
                if (N <= suml) break;
                var count = (int)((N - suml) / item.Value);
                suml += count * item.Value;
                sumMoney += (BigInteger)count * (BigInteger)item.Key;
            }
            Console.WriteLine(sumMoney);
        }
    }