Problem:
Score : 300 points

Problem Statement

There are N candles placed on a number line.
The i-th candle from the left is placed on coordinate x_i.
Here, x_1 < x_2 < ... < x_N holds.

Initially, no candles are burning.
Snuke decides to light K of the N candles.

Now, he is at coordinate 0.
He can move left and right along the line with speed 1.
He can also light a candle when he is at the same position as the candle, in negligible time.

Find the minimum time required to light K candles.

Constraints

1 \leq N \leq 10^5

1 \leq K \leq N

x_i is an integer.

|x_i| \leq 10^8

x_1 < x_2 < ... < x_N

Input

Input is given from Standard Input in the following format:

N K
x_1 x_2 ... x_N

Output

Print the minimum time required to light K candles.

Sample Input 1

5 3
-30 -10 10 20 50

Sample Output 1

40

He should move and light candles as follows:

Move from coordinate 0 to -10.

Light the second candle from the left.

Move from coordinate -10 to 10.

Light the third candle from the left.

Move from coordinate 10 to 20.

Light the fourth candle from the left.

Sample Input 2

3 2
10 20 30

Sample Output 2

20

Sample Input 3

1 1
0

Sample Output 3

0

There may be a candle placed at coordinate 0.

Sample Input 4

8 5
-9 -7 -4 -3 1 2 3 4

Sample Output 4

10

Solution in Rust (1.42.0) (judge verdict: Accepted)

#![allow(non_snake_case)]

use std::io::{stdin, Read};
use std::str::FromStr;
fn read_option<T: FromStr>() -> Option<T> {
    let stdin = stdin();
    let stdin = stdin.lock();
    let token: String = stdin
        .bytes()
        .map(|c| c.expect("failed to read char") as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect();
    token.parse().ok()
}
fn read<T: FromStr>() -> T {
    let opt = read_option();
    opt.expect("failed to parse token")
}

fn main() {
    let mut N: usize = read();
    let mut K: usize = read();
    let mut minuses = vec![];
    let mut pluses = vec![];
    for _ in 0..N {
        let val: i32 = read();
        match val.cmp(&0) {
            std::cmp::Ordering::Equal => {
                N -= 1;
                K -= 1;
            }
            std::cmp::Ordering::Less => {
                minuses.push(-val as u64);
            }
            std::cmp::Ordering::Greater => {
                pluses.push(val as u64);
            }
        }
    }
    if K == 0 {
        println!("0");
        return;
    }
    minuses.reverse();
    let mut ans = std::u64::MAX;
    for (one, another) in &[(&minuses, &pluses), (&pluses, &minuses)] {
        for (i, &v) in one.iter().enumerate() {
            if K == i + 1 {
                ans = std::cmp::min(ans, v);
                break;
            }
            if K - i - 1 > another.len() {
                continue;
            }
            // dbg!(K, i, v, K - i - 2, another[K - i - 2]);
            ans = std::cmp::min(ans, v * 2 + another[K - i - 2]);
        }
    }
    println!("{}", ans);
}