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 <iomanip>
#include <algorithm>
#include <numeric>
#include <cmath>
#include <vector>
#include <list>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <tuple>
using namespace std;

int main(){

    int n, k; cin >> n >> k;

    vector<int> vneg, vpos;
    int temp;
    for(int i=0; i<n; i++){
        cin >> temp;
        if(temp < 0){
            vneg.insert(vneg.begin(), abs(temp));
        }
        else{
            vpos.push_back(temp);
        }
    }

    if(vneg.size() == 0) vneg.push_back(1e9);
    if(vpos.size() == 0) vpos.push_back(1e9);

    vector<int> vneg2, vpos2;
    for(int i=0; i<vneg.size(); i++){
        vneg2.push_back(vneg[i]*2);
    }
    for(int i=0; i<vpos.size(); i++){
        vpos2.push_back(vneg[i]*2);
    }

    // for(int i=0; i<vneg.size(); i++){
    //     cout << vneg[i] << endl;
    // }
    // cout << endl;
    // for(int i=0; i<vneg2.size(); i++){
    //     cout << vneg2[i] << endl;
    // }

    int cnt = 0;
    int i_vneg = 0;
    int ans1 = 0;
    int i_vpos = 0;
    int ans2 = 0;

    while(cnt < k){
        if(vneg2[i_vneg] < vpos[i_vpos]){
            ans1 = vneg2[i_vneg];
            i_vneg++;
        }
        else{
            ans2 = vpos[i_vpos];
            i_vpos++;
        }
        cnt++;
    }
    int ans = ans1 + ans2;

    cnt = 0;
    i_vneg = 0;
    ans1 = 0;
    i_vpos = 0;
    ans2 = 0;

    while(cnt < k){
        if(vneg[i_vneg] < vpos2[i_vpos]){
            ans1 = vneg[i_vneg];
            i_vneg++;
        }
        else{
            ans2 = vpos2[i_vpos];
            i_vpos++;
        }
        cnt++;
    }

    if(ans1 + ans2 < ans){
        ans = ans1 + ans2;
    }

    cout << ans << endl;

    return 0;
}