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: Wrong Answer)

/* Murad Eynizade */

#include <bits/stdc++.h>
#define intt long long
#define FAST_READ ios_base::sync_with_stdio(0);cin.tie(0);
#define SIZE 100001
#define INF INT_MAX
#define F first
#define S second
#define in(a) scanf("%d",&a);
#define outn(a) printf("%d\n",&a);
#define outs(a) printf("%d ",&a);


using namespace std;

int a[100005];

int main()
{
    FAST_READ;
    int n , k;
    cin>>n>>k;
    for (int i = 0;i<n;i++)cin>>a[i];
    int in = 0;
    vector< int >neg,pos;
    while (a[in] <= 0 && in < n) {
        if (a[in] == 0) {
            k--;
            in++;
            break;
        }
        neg.push_back(abs(a[in]));
        in++;
    }
    reverse(neg.begin(),neg.end());
    while (in < n) {
        pos.push_back(a[in]);
        in++;
    }
    int sz = neg.size();
    int sz1 = pos.size();
    if (k == 0) {
        cout<<0<<endl;
        return 0;
    }
    if (sz == 0)cout<<pos[k - 1];
    else if (sz1 == 0)cout<<neg[sz - k]<<endl;
    else {
        int ans = INF;
        for (int i = 0;i<=k;i++) {
            if (i == 0 && sz1 >= k)ans = min(ans,pos[k - 1]);
            else if (i == k && sz >= k)ans = min(ans,neg[k - 1]);
            if (i > sz1 || k - i > sz)continue;
            else {
                ans = min(ans,pos[i - 1] + neg[k - i - 1] + min(pos[i - 1],neg[k - i - 1]));
            }
        }
        cout<<ans<<endl;
    }
    return 0;
}