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 static System.Console;
using System.Runtime.CompilerServices;
using static MyUtil;

class MyUtil
{
    public static int[] ReadIntArray()
    {
	return ReadLine().Split().Select(x => int.Parse(x)).ToArray();
    }
}

class Program
{
    public static void Main()
    {
	var tmp = ReadIntArray();
	int q = tmp[0], h = tmp[1], s = tmp[2], d = tmp[3];
	long n = int.Parse(ReadLine()) * 4;

	Tuple<int,int>[] ps = { new Tuple<int, int>(q*8, 1),
				new Tuple<int, int>(h*4, 2),
				new Tuple<int, int>(s*2, 4),
				new Tuple<int, int>(d  , 8)};
	Array.Sort(ps);

	long totalPrise = 0;
	
	for(int i = 0; i < 4; i++)
	{
	    Tuple<int, int> p = ps[i];
	    long prisePerDouble = p.Item1;
	    int nUnit = p.Item2;
	    long prise = prisePerDouble / (8 / nUnit);

	    while (n >= nUnit)
	    {
		n -= nUnit;
		totalPrise += prise;
	    }
	}

	WriteLine(totalPrise);
    }
}