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 <bits/stdc++.h>
#define pb push_back
#define REP(i, n) for (signed long long i = 0; i < (n); i++)
#define MOD 998244353
#define INF 93193111451418101
#define bitcnt(a) (ll) __builtin_popcount((a))
#define lb(a, b) lower_bound((a).begin(), (a).end(), (b))
#define ub(a, b) upper_bound((a).begin(), (a).end(), (b))
using namespace std;
typedef long long ll;
typedef pair<ll, ll> P;
typedef pair<string, string> PS;

ll m[114514] = {}, M[114514];
int main() {
  ll n, k;
  cin >> n >> k;

  REP(i, n) {
    ll aa;
    cin >> aa;
    if (aa > 113112) {
      continue;
    }
    if (aa < 0) {
      m[abs(aa)]++;
    } else {
      M[aa]++;
    }
  }
  REP(i, 113514) {
    m[i + 1] += m[i];
    M[i + 1] += M[i];
  }
  ll ret = INF;
  m[113319] = INF;
  REP(i, 114513) {
    ret = min(ret, lower_bound(m, m + 113413, max((ll)0, k - M[i])) - m + i * 2);

    ret = min(ret, (lower_bound(m, m + 113413, max((ll)0, k - M[i])) - m) * 2 + i);
  }
  cout << ret << endl;
}