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.*;
import java.util.Map.Entry;
 
class Main {
	 static int mod =  (int) (Math.pow(10,9)+7);
	 static int[] ans;
//	 static int mod = 998244353;
   public static void main(String[] args) {
	          
	   Scanner sc = new Scanner(System.in);
       int  N = sc.nextInt();
       int  K = sc.nextInt();
       long[] a = new long[N+1];
       long max=0;
       boolean flg=false;
       int cn=0;
       int t=0;
       for (int i=0 ; i<N; i++) {
           long tmp = Long.parseLong(sc.next());
           if(tmp<0) {
        	   tmp=tmp*-2;
           } else {
        	   if(flg==false) {
        		   if(tmp==0) {
        			   K--;
        			   flg=true;
        			   cn=t;
        		   } else {
            		   cn=t;
            		   a[t]=0;
            		   t++;
            		   flg=true;        			   
        		   }
        	   }
           }
           a[t]=tmp;
           t++;
       }
       if(flg==false) {
    	   a[t]=0;
    	   t++;
       }
       Long min=Long.MAX_VALUE;
       for(int i=0;i<t;i++) {
    	   if(cn+K-i>t-1)continue;
    	   if(cn-i<0)continue;
    	   min=Math.min(min, a[cn+K-i]+a[cn-i]);
       }
       System.out.println(min); 
       return;
   }

}