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;
typedef long long ll;
int x[100500];
void solve() {
	int n, k;
	cin >> n >> k;
	for (int i = 0; i < n; i++) {
		cin >> x[i];
	}

	ll res = LONG_MAX;
	map<ll, ll> mp1, mp2, m1, m2;
	ll k1 = 0, k2 = 0;
	for (int i = 0; i < n; i++) {
		if (x[i] > 0) {
			k1++;
			mp1[x[i]] = k1;
			m1[k1] = x[i];
		}
		if (x[n - i - 1] <= 0) {
			k2++;
			mp2[x[n - i - 1]] = k2;
			m2[k2] = x[n - i - 1];
		}
	}
	for (int i = 0; i < n; i++) {
		if (x[i] <= 0)  {
			ll need = k - mp2[x[i]];
			res = min(res, -x[i] + (need > 0) * ((-x[i]) + m1[need]));
		}
		else {
			ll need = k - mp1[x[i]];
			res = min(res, x[i] + (need > 0) * (x[i] - m2[need]));
		}
	}
	cout << res;
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	int t = 1;
	//cin >> t;
	for (int i = 1; i <= t; i++) {
		solve();
	}
}