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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <cstdio>
int main() {
  long long A, B, C, D, N;
  long long ans = 0;
  scanf("%lld %lld %lld %lld %lld", &A, &B, &C, &D, &N)+1;
  long long MIN2 = A * 8;
  if (B*4 < MIN2) MIN2 = B*4;
  if (C*2 < MIN2) MIN2 = C*2;
  if (D < MIN2) MIN2 = D;
  ans += (N / 2) * MIN2;
  N = N % 2;
  
  long long MIN1 = A * 4;
  if (B*2 < MIN1) MIN1 = B*2;
  if (C < MIN1) MIN1 = C;
  
  if (N == 1) ans += MIN1;
  
  printf("%lld", ans);
  return 0;
}