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)]
#![allow(unused_imports)]
#![allow(dead_code)]

use proconio::{input, fastout};
use proconio::marker::*;
use whiteread::parse_line;
use std::collections::*;
use num::*;
use num_traits::*;
use superslice::*;
use std::ops::*;

use itertools::Itertools;
use itertools_num::ItertoolsNum;


#[fastout]
fn solve() {
    const MOD: usize = 1_000_000_007;
    const INF: usize = std::usize::MAX;
    
    input!{
        n: usize, k: usize,
        x_vec: [isize; n]
    }

    let pos = x_vec.iter().filter(|&x| *x >= 0).map(|x| *x).collect::<Vec<isize>>();
    let neg = x_vec.iter().filter(|&x| *x < 0).map(|x| *x).rev().collect::<Vec<isize>>();

    let mut ans = std::isize::MAX;

    // pos negをどこで区切るか
    for i in 0..=k {
        let pos_cnt = i;
        let neg_cnt = k-i;
        if pos_cnt > pos.len() || neg_cnt > neg.len() { continue; }
        
        let pos_cost = if pos_cnt == 0 { 0 } else { pos[pos_cnt-1] };
        let neg_cost = if neg_cnt == 0 { 0 } else { neg[neg_cnt-1] };
        let cost = std::cmp::min(pos_cost*2 + neg_cost.abs(), neg_cost.abs()*2 + pos_cost);
        ans = std::cmp::min(ans, cost)
    }

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

fn main() {
    solve()
}

#[cfg(test)]
mod test {
    use super::solve;
}