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: Accepted)

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

class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int k = sc.nextInt();
		int[] x = new int[n];
		List<Integer> negList = new ArrayList<>();
		List<Integer> posList = new ArrayList<>();
		for (int i = 0; i < n; i++) {
			x[i] = sc.nextInt();
			if (x[i] == 0) {
				k--;
			}
			if (x[i] < 0) {
				negList.add(x[i] * -1);
			} else if (x[i] > 0) {
				posList.add(x[i]);
			}
		}
		Collections.sort(negList);
		int negnum = negList.size();
		int posnum = posList.size();
		int count = 300000000;
		int temp = 0;
		int negtemp = 0;
		int postemp = 0;
		int range = 0;
		int negrange = 0;
		int posrange = 0;
		if (negnum <= k) {
			negrange += negnum;
		} else {
			negrange += k;
		}
		if (posnum <= k) {
			posrange += posnum;
		} else {
			posrange += k;
		}
		range = negrange + posrange;
		for (int i = 0; i < range-k+1; i++) {
			if (negrange - i - 1 >= 0) {
				negtemp = negList.get(negrange - i - 1);
			} else {
				negtemp = 0;
			}
			if (negrange - i < k) {
				postemp = posList.get(k - (negrange - i) - 1);
			} else {
				postemp = 0;
			}
			temp = (Math.min(negtemp, postemp) * 2) + Math.max(negtemp, postemp);
			if (temp < count) {
				count = temp;
			}
		}
		System.out.println(count);
	}
}