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: Wrong Answer)

#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
#define pb push_back
#define mp make_pair

using ll = long long;
using namespace std;

void solve() {
    vector<ll> a;
    ll n, k;
    cin>>n>>k;
    for(int i=0;i<n;i++){
        ll num;
        cin>>num;
        a.push_back(num);
    }
    ll m=LONG_LONG_MAX;
    for(int i = 0; i<=n-k;i++){
        ll l=i, r = l+k-1;
        ll k = min(abs(a[i]), abs(a[l]));
        m = min(k+abs(a[r]-a[l]), m);
    }
    cout<<abs(m)<<'\n';

}

int main() 
{
    std::ios::sync_with_stdio(false); \
        std::cin.tie(NULL);
    int test;
    test=1;
    while (test--) {
        solve();
    }
    return 0;
}