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 Rust (1.15.1) (judge verdict: Accepted)

use std::io::{self,Read};

fn main() {
    let mut input = String::new();
    io::stdin().read_to_string(&mut input).expect("i/o error");
    let mut iter = input.split_whitespace();

    macro_rules! RD { () => ( iter.next().unwrap().parse().unwrap() ) }

    let coef  = [8i64, 4, 2, 1];
    let mut v = [0i64; 4];
    for (e, c) in v.iter_mut().zip(coef.iter()) {
        *e  = RD!();
        *e *= *c;
    }
    let n: i64 = RD!();

    let mut ans = 0;
    ans += n/2 * v.iter().min().unwrap();
    ans += n%2 * v[..3].iter().min().unwrap() / 2;

    println!("{}", ans);
}