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 (1.15.1) (judge verdict: Accepted)

use std::cmp;
use std::io;

#[allow(unused_macros)]
macro_rules! input {
    ( $($x:expr ),*) => {
        {
            let temp_str = input_line_str();
            let mut split_result_iter = temp_str.split_whitespace();
                $(
                let buf_split_result = split_result_iter.next();
                let buf_split_result = buf_split_result.unwrap();
                    ($x) = buf_split_result.parse().unwrap();
                )*
        }
    };
}

#[allow(dead_code)]
fn input_line_str() -> String {
    let mut s = String::new();
    io::stdin().read_line(&mut s).unwrap();
    s.trim().to_string()
}

#[allow(dead_code)]
fn input_vector<T>(line: usize) -> Vec<Vec<T>>
where
    T: std::str::FromStr,
{
    let mut v: Vec<Vec<T>> = Vec::new();

    for _ in 0..line {
        let s = input_line_str();
        let split_result = s.split_whitespace();
        let mut vec_line: Vec<T> = Vec::new();
        for z in split_result {
            let buf = match z.parse() {
                Ok(r) => r,
                Err(_) => panic!("Parse Error"),
            };
            vec_line.push(buf);
        }
        v.push(vec_line);
    }
    v
}

fn main() {
    let n: isize;
    let k: isize;
    input!(n, k);
    let mut vplus: Vec<isize> = Vec::new();
    let mut vminus: Vec<isize> = Vec::new();
    let mut plusnum: usize = 0;
    let mut minusnum: usize = 0;
    let mut zero = 0;
    let mut ans = 999999999999;

    let mut str_line = input_line_str();
    let mut str_split = str_line.split_whitespace();

    for i in 0..n {
        let l: isize;
        l = str_split.next().unwrap().parse().unwrap();
        if l > 0 {
            plusnum += 1;
            vplus.push(l);
        } else if l < 0 {
            minusnum += 1;
            vminus.push(-1 * l);
        } else {
            zero += 1;
        }
    }

    if zero == 1 && plusnum == 0 && minusnum == 0 {
        ans = 0;
    }

    for (i, x) in vplus.iter().enumerate() {
        let rest = k - (i as isize) - 1 - zero;
        if (rest as usize) < 0 {
            break;
        } else if (rest as usize) == 0 {
            ans = cmp::min(ans, *x);
            break;
        }

        if (rest as usize) <= minusnum {
            ans = cmp::min(ans, 2 * *x + vminus[minusnum - (rest as usize)]);
        }
    }
    for (i, x) in vminus.iter().rev().enumerate() {
        let rest = k - (i as isize) - 1 - zero;
        if (rest as usize) < 0 {
            break;
        } else if (rest as usize) == 0 {
            ans = cmp::min(ans, *x);
            break;
        }
        if (rest as usize) <= plusnum {
            ans = cmp::min(ans, 2 * *x + vplus[(rest as usize) - 1]);
        }
    }

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