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 {
	public static void main(String[] args){

		Scanner sc = new Scanner(System.in);
		// 整数の入力
		int n = sc.nextInt();
		int k = sc.nextInt();
		//String s = sc.next();
		/*
		List<Integer> list = new ArrayList<>();
		for(int i=0;i<n;i++) {
			list.add(sc.nextInt());
		}
		Collections.sort(list);*/
		int[] x = new int[n];


		for(int i=0;i<n;i++) {
			x[i] = sc.nextInt();
		}

		//boolean flag = true;
		int currentBest = 300000000;

		for(int i=0;i<n-k+1;i++) {
			if(x[i+k-1]<=0) {
				if(currentBest>Math.abs(x[i])) {
					currentBest = Math.abs(x[i]);
				}
			}else {
				if(x[i]>=0) {
					if(currentBest>Math.abs(x[i+k-1])) {
						currentBest = Math.abs(x[i+k-1]);
					}
				}else {
					int a = Math.max(Math.abs(x[i]), Math.abs(x[i+k-1]));
					a += Math.min(Math.abs(x[i]), Math.abs(x[i+k-1]))*2;
					if(currentBest>a) {
						currentBest = a;
					}
				}
			}



		}
		System.out.println(currentBest);
	}
	/*
	static boolean check(int t,int x,int y) {
		if(Math.abs(x)+Math.abs(y)>t)return false;
		if((Math.abs(x)+Math.abs(y)-t)%2==0) {
			return true;
		}else {
			return false;
		}

	}
	*/
}