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::{BufRead, Write};
use std::io;
use std::cmp::min;

fn solve<R: BufRead, W: Write>(mut input: R, mut output: W) {
    let mut buf = String::new();
    input.read_line(&mut buf).unwrap();
    let (q, h, s, d): (usize, usize, usize, usize) = {
        let mut split = buf.split_whitespace();
        let a = split.next().unwrap().parse().unwrap();
        let b = split.next().unwrap().parse().unwrap();
        let c = split.next().unwrap().parse().unwrap();
        let d = split.next().unwrap().parse().unwrap();
        (a, b, c, d)
    };
    buf.clear();
    input.read_line(&mut buf).unwrap();
    let n: usize = buf.trim().parse().unwrap();
    let one_liter = min(q * 4, min(h * 2, s));
    let two_liters = d;
    let price = if one_liter * 2 < two_liters {
        one_liter * n
    } else {
        n / 2 * two_liters + n % 2 * one_liter
    };
    writeln!(output, "{}", price).unwrap();
}

fn main() {
    let stdin = io::stdin();
    let stdout = io::stdout();
    solve(stdin.lock(), stdout.lock());
}

#[cfg(test)]
mod tests {
    fn test(input: &str, output: &str) {
        let mut v: Vec<u8> = Vec::new();
        ::solve(input.as_bytes(), &mut v);
        assert_eq!(String::from_utf8(v).unwrap(), output);
    }

    #[test]
    fn case1() {
        test(
            "20 30 70 90
3\n",
            "150\n",
        );
    }
    #[test]
    fn case2() {
        test(
            "10000 1000 100 10
1\n",
            "100\n",
        );
    }
    #[test]
    fn case3() {
        test(
            "10 100 1000 10000
1\n",
            "40\n",
        );
    }
    #[test]
    fn case4() {
        test(
            "12345678 87654321 12345678 87654321
123456789\n",
            "1524157763907942\n",
        );
    }
}