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: Wrong Answer)

import java.util.*;

class Main{
	public static void main(String args[]){
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int k = sc.nextInt();
		ArrayList<Integer> plist = new ArrayList<Integer>();
		ArrayList<Integer> mlist = new ArrayList<Integer>();
		for(int i = 0; i < n ; i++){
			int x = sc.nextInt();
			if(x >= 0){
				plist.add(x);
			}else{
				mlist.add(x);
			}
		}
		Collections.sort(plist);
		Collections.sort(mlist);
		Collections.reverse(mlist);
		int ansa = 0;
		if(plist.isEmpty()){
			ansa = Math.abs(mlist.get(k-1));
		}else if(mlist.isEmpty()){
			ansa = plist.get(k-1);
		}else{
			int ansb = 0;
			int phoz = 1000000000;
			int mhoz = 1000000000;
			if(plist.size() >= k){
				phoz = plist.get(k-1);
			}
			if(mlist.size() >= k){
				mhoz = mlist.get(k-1);
			}
			for(int i = 0; i < k; i++){
				if(plist.isEmpty()){
					ansb = Math.abs(mlist.get(0));
					mlist.remove(0);
				}else if(mlist.isEmpty()){
					ansa = plist.get(0);
					plist.remove(0);
				}else{
					if(plist.get(0) <= Math.abs(mlist.get(0))){
						ansa = plist.get(0);
						plist.remove(0);
					}else{
						ansb = Math.abs(mlist.get(0));
						mlist.remove(0);
					}
				}
			}
			ansa = Math.min(ansa,ansb)*2+Math.max(ansa,ansb);
			ansa = Math.min(ansa,phoz);
			ansa = Math.min(ansa,mhoz);
		}
		System.out.print(ansa);
	}
}