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 JavaScript (node.js v5.12) (judge verdict: Accepted)

function Main(input) {
  input = input.split("\n");
  var n = parseInt(input[0].split(" ")[0]);
  var k = parseInt(input[0].split(" ")[1]);
  x = new Array(n).fill(0);
  tmp = input[1].split(" ");
  var plus=0;
  var minus=0;
  for(i=0;i<n;i++){
    x[i]=parseInt(tmp[i]);
    if(x[i]>0){
      plus++;
    }else if(x[i]<0){
      minus++;
    }
  }
  var ans=Math.pow(10,9)+7;
  if(x.indexOf(0)!=-1){
    n-=1;
    k-=1;
    x.splice(x.indexOf(0),1);
  }
  if(x.length==0){
    ans=0;
  }else{
    for(i=0;i<n-k+1;i++){
      if(x[i]<0&&x[i+k-1]>0){
        ans=Math.min(ans,Math.abs(x[i])*2+x[i+k-1],Math.abs(x[i])+x[i+k-1]*2);
      }else if(i==minus-k){
        ans=Math.min(ans,Math.abs(x[i]));
      }else if(i==minus){
        ans=Math.min(ans,x[i+k-1]);
      }
    }
  }
  console.log('%s', ans);
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));