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)

#include <bits/stdc++.h>

using namespace std;

#define vi vector<int>
#define all(v) v.begin(),v.end()
#define ll long long int
#define IOS ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
#define D1(x) {cerr<<" [" <<#x<<": "<<x<<"]";cout << endl;}
#define D2(x) {cerr<<" [" <<#x<<": ";for(auto it:x)cerr<<it<< " ";cerr<<"] ";cout << endl;}

const ll MOD = 1e9 + 7;
const ll maxn = 2e5 + 5;
const ll INF = 1e18;

void solve(){
    int n,k;
    cin >> n >> k;
    ll ans = INF;
    vector<ll> v(n);
    for(int i=0;i<n;i++)cin >> v[i];
    for(int i=0;i+k<=n;i++){
	ll l = v[i];
	ll r = v[k+i-1];
	if(l>=0){
		ans = min(ans,r);
	}
	else if(r<=0){
		ans = min(ans,-l);
	}
	else{
	       ans = min({ans,2*r - l,2*(-l)+r});
	
	}
	cout  << ans;
}

}
int main() {
    IOS
        solve();
    cerr << endl << "[ Time : " << (float) clock() / CLOCKS_PER_SEC << " secs ]" << endl;

}
// integer overflow
// remember to clear visited array
// take input as vector<string> while using grid
// don't assign after modifying