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.Scanner;
public class Main {

	static int N, K,MIN = 999999999,INDEX0,START,END;
	static int[] initArr, num_line;
	static boolean has0;
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		N = sc.nextInt();
		K = sc.nextInt();
		initArr = new int[N];
		num_line = new int[N + 1];
		for (int i = 0; i < N; i++) {
			initArr[i] = sc.nextInt();
			if(initArr[i] == 0) {
				INDEX0 = i;
				has0 = true;
			}
		}
		if(!has0) {
			boolean flagZ = false;
			boolean flagF = false;
			if (initArr[0] > 0) {
				INDEX0 = 0;
				num_line[0] = 0;
				flagZ = true;
			}
			if (initArr[N - 1] < 0) {
				INDEX0 = N;
				num_line[N] = 0;
				flagF = true;
			}
			if (!flagZ && !flagF) {
				for (int i = 0; i < initArr.length; i++) {
					int temp = initArr[i + 1];
					if (temp > 0) {
						INDEX0 = i + 1;
						num_line[i] = 0;
						break;
					}
				}
			}
			for (int i = 0; i < N; i++) {
				if (flagF) {
					num_line[i] = initArr[i];
				} else if (flagZ) {
					num_line[i + 1] = initArr[i];
				} else {
					int temp = initArr[i];
					if (temp < 0) {
						num_line[i] = temp;
					} else {
						num_line[i + 1] = temp;
					}
				}
			}
		}else {
			num_line = initArr;
		}
		if(INDEX0 == 0) {
			START = 0;
			END = K;
		}else if (INDEX0 == N) {
			START = N - K;
			END = N;
		}else {
			START = INDEX0 > K ? INDEX0 - K : 0;
			END = (N - INDEX0) > K ? INDEX0 + K : N;
		}
		if(has0) {
			END--;
			K--;
		}
		for (int i = START; i <= END - K; i++) {
			int left = Math.abs(num_line[i]);
			int right = Math.abs(num_line[i + K]);
			int min = left < right ? left : right;
			int size = left + right + min;
			MIN = size < MIN ? size : MIN;
		}
		System.out.println(MIN);
	}
}