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::stdin;

fn main() {
    let mut buf = String::new();
    stdin().read_line(&mut buf).ok();
    let qhsd =  buf.split_whitespace().map(|x| x.parse().ok().unwrap()).collect::<Vec<u64>>();
    let mut buf = String::new();
    stdin().read_line(&mut buf).ok();
    let n: u64 = buf.trim().parse().ok().unwrap();

    // println!("{:?}", qhsd);
    // println!("{}", n);

    let mut qhsd: Vec<(u64, u64)> = [1, 2, 4, 8].iter().cloned().zip(qhsd).collect();
    qhsd.sort_by_key(|t| t.1 * (8 / t.0));

    let mut rest = 4 * n;
    let mut cost = 0u64;

    if rest != 0 {
        let cop = rest;
        rest -= (cop / qhsd[0].0) * qhsd[0].0;
        cost += (cop / qhsd[0].0) * qhsd[0].1;
    }
    if rest != 0 {
        let cop = rest;
        rest -= (cop / qhsd[1].0) * qhsd[1].0;
        cost += (cop / qhsd[1].0) * qhsd[1].1;
    }
    if rest != 0 {
        let cop = rest;
        rest -= (cop / qhsd[2].0) * qhsd[2].0;
        cost += (cop / qhsd[2].0) * qhsd[2].1;
    }
    if rest != 0 {
        let cop = rest;
        rest -= (cop / qhsd[3].0) * qhsd[3].0;
        cost += (cop / qhsd[3].0) * qhsd[3].1;
    }

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