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 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>
#include<stdlib.h>
#include<math.h>
#include<string.h> 
#include<limits.h>
#include <stdbool.h>
typedef   long long ll;
#define MOD 10e9+7  //10億　= 10^9
#define length 100000+3000 //10万
#define kw_len 10+2
#define INF 16446000000009000
#define pi 3.1415926535897932384
ll can[100000];
int main(){
    ll N,K,sum=INF,temp=0;    
    bool flag=false,flag2=false;
    scanf("%llu%llu",&N,&K);
    for(int i=0;i<N;i++){
        scanf("%lld",can+i);
    }
    for(int i=0;i<N-K;i++){
        temp=0;
        flag=false;
        temp += llabs(*(can+i));

        for(int j=i+1;j<K;j++){
            temp += llabs(llabs(*(can+j))-llabs(*(can+j-1)));
            if(*(can+j)<0)flag=true;
            if(flag){if(*(can+j)>0){flag2=true;
            }}
        }
        
        if(flag2){
            temp = llabs(*(can+i));
        }
        
        if(temp<=sum){
            sum=temp;
        }
    }
    printf("%lld",sum);
}