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 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<stdio.h>

int main(){
  int q, h, s, d, k, a[4], cost = 0;
  float b[4], n, c;
  
  scanf("%d %d %d %d",&q, &h, &s, &d);
  scanf("%f", &n);
  
  a[0] = q*8; b[0] = 0.25;
  a[1] = h*4; b[1] = 0.5;  /*a金額,bサイズ*/
  a[2] = s*2; b[2] = 1;
  a[3] = d;   b[3] = 2;
  for(int i = 0; i < 4; i++){
    for(int j = i; j < 4; j++){
      if(a[i] > a[j]){
        c = a[i];
        a[i] = a[j];
        a[j] = c;
        c = b[i];
        b[i] = b[j];
        b[j] = c;
      }
    }
  }
  k = 0;
  while(n > 0){
    if(n >= b[k]){
      cost = cost + (float)a[k]*b[k]/2;
      n = n - b[k];
    } else {
      k++;
      if(k == 4){
        break;
      }
    }
  }
  printf("%d\n", cost);
}