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 C++ (GCC 9.2.1) (judge verdict: Accepted)

#include<bits/stdc++.h>
using namespace std;
int n,c,x,a,b,p,q,mn=1e9;
vector<int> l,r;
int main()
{
	l.push_back(0);
	r.push_back(0);
	scanf("%d%d",&n,&c);
	for(int i=1;i<=n;i++)
	{
		scanf("%d",&x);
		if(x>=0)
		{
			r.push_back(x);
		}else
		{
			l.push_back(-x);
		}
	}
	sort(l.begin(),l.end());
	sort(r.begin(),r.end());
	a=l.size()-1;
	b=r.size()-1;
	for(int i=0;i<=c;i++)
	{
		p=i;
		q=c-i;
		if(p<=a&&q<=b)
		{
			mn=min(mn,min(l[p],r[q])+r[q]+l[p]);
		}
	}
	printf("%d\n",mn);
}