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: Wrong Answer)

'use strict'
function main(input) {
  let ans = 0
  let prev = []
  let next = []
  let mP = []
  let mN = []
  const calc = (p, n) => p > n ? p + n * 2 : n + p * 2

  input = input.trim().split('\n')
  const NM = input[0].split(' ').map(v => v - 0)
  input[1].split(' ').forEach(v => {
    let n = v - 0
    if (n === 0) {
      NM[1]--
    } else {
      n < 0 ? prev.unshift(n*-1) : next.push(n)
    }
  })

  if (next.length <= NM[1]) {
    mN = [...next]
    NM[1] -= next.length
  } else {
    for (let i = 0; i < NM[1]; i++) {
      mN.push(next.shift())
    }
    NM[1] = 0
  }
  for (let i = 0; i < NM[1]; i++) {
    mP.push(prev.shift())
  }

  ans = calc(mP[mP.length - 1] || 0, mN[mN.length - 1] || 0)

  while (mN.length && prev.length) {
    let c = calc(prev[0], mN[mN.length - 2] || 0)
    if (c < ans) {
      mP.push(prev.shift())
      mN.pop()
      ans = c
    } else {
      break
    }
  }

  console.log(ans)
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));