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++14 (GCC 5.4.1) (judge verdict: Runtime Error)

#include <iostream>
#include <vector>
#include <algorithm>
#define llint long long
#define inf 1e18

using namespace std;

llint n, k;
llint x[100005];
vector<llint> pvec, mvec;

int main()
{
    cin >> n >> k;
    for(int i = 0; i < n; i++) cin>>x[i];
    
    for(int i = 0; i < n; i++){
        if(x[i] >= 0) pvec.push_back(x[i]);
        else mvec.push_back(-x[i]);
    }
    reverse(mvec.begin(), mvec.end());
    
    llint ans = inf;
    if(pvec.size() > k-1) ans = min(ans, pvec[k-1]);
    for(int i = 0; i < mvec.size(); i++){
        if(k-i-2 >= 0 && k-i-2 < pvec.size()) ans = min(ans, mvec[i] * 2 + pvec[k-i-2]);
        if(k-i-2 >= 0 && k-i-2 < mvec.size()) ans = min(ans, mvec[i] + 2 * pvec[k-i-2]);
    }
    cout << ans <<endl;
   return 0;
}