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 Java8 (OpenJDK 1.8.0) (judge verdict: Runtime Error)

import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int K = sc.nextInt();

		ArrayList<Long> right = new ArrayList<>();
		ArrayList<Long> left = new ArrayList<>();

		for (int i = 0; i < N; i++) {
			long x = sc.nextLong();
			if (x>0) {
				right.add(x);
			} else if(x==0) {
				K--;
			} else {
				left.add(-x);
			}
		}
		right.add(0L);
		left.add(0L);

		Collections.sort(right);
		Collections.sort(left);

		long ans = Long.MAX_VALUE;

		//正からi点、負からK-i点取る
		for (int i = 0; i < right.size(); i++) {
			int j = K - i;
			if (j >= 0 && j < left.size()) {
				long min = Math.min(right.get(i), left.get(K-i));
				long max = Math.max(right.get(i), left.get(K-i));

				ans = Math.min(ans , min*2 + max);
			}
		}
		//負からi点、正からK-i点取る
		for (int i = 0; i < left.size(); i++) {
			int j = K - i;
			if (j >= 0 && j < left.size()) {
				long min = Math.min(left.get(i), right.get(K-i));
				long max = Math.max(left.get(i), right.get(K-i));

				ans = Math.min(ans, min*2 + max);
			}
		}
		System.out.println(ans);
	}
}