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)

fn main() {
    let mut a: Vec<usize> =
        io::read_line().split_whitespace().map(|num| num.parse().unwrap()).collect();
    let n: usize = io::readln();
    let mut two = [a[0] * 8, a[1] * 4, a[2] * 2, a[3]];
    let mut one = [a[0] * 4, a[1] * 2, a[2]];
    one.sort();
    two.sort();
    let mut ans: usize = 0;
    if n > 1 {
        ans = two[0] * (n / 2);
        if n % 2 != 0 {
            ans += one[0];
        }
    } else {
        ans = one[0];
    }
    println!("{}", ans);
}

pub mod io {
    use std::io;

    pub fn read_line() -> String {
        let mut s = String::new();
        io::stdin().read_line(&mut s).unwrap();
        s.trim_right().to_owned()
    }

    pub fn readln<T: Read>() -> T {
        let mut s = String::new();
        io::stdin().read_line(&mut s).unwrap();
        T::read(s.trim())
    }

    pub trait Read {
        fn read(s: &str) -> Self;
    }

    impl Read for String {
        fn read(s: &str) -> Self {
            s.to_string()
        }
    }

    impl<T: Read> Read for Vec<T> {
        fn read(s: &str) -> Self {
            s.split_whitespace().map(|w| T::read(w)).collect()
        }
    }

    macro_rules !def_read {
        ($t : ty) => {
            impl Read for $t {
                fn read(s : &str)->$t { s.parse().unwrap() }
            }
        }
    }

    macro_rules !def_read_tuple {
        ($($t : ident), *) => {
            impl<$($t : Read + Default), *> Read for ($($t), *) {
                fn read(s : &str)->Self {
                    let mut iter = s.split_whitespace();
                    ($($t::read(iter.next().unwrap())), *)
                }
            }
        };
    }

    def_read!(i32);
    def_read!(i64);
    def_read!(isize);
    def_read!(usize);
    def_read!(f32);
    def_read!(f64);
    def_read_tuple!(T0, T1);
    def_read_tuple!(T0, T1, T2);
    def_read_tuple!(T0, T1, T2, T3);
    def_read_tuple!(T0, T1, T2, T3, T4);
}