#include <stdio.h>
#include <stdlib.h>
#include <math.h>
int main(){
  int n, m, *d, *r, result=10000000;
  int i,buff;
  int left,right;
  
  scanf("%d %d",&n,&m);
  
  d=(int*)malloc(sizeof(int)*m);
  r=(int*)malloc(sizeof(int)*(m-n+1));
  for(i=0;i<m;i++){
    scanf("%d",&d[i]);
  }
  for(i=0;i<m-n+1;i++){
    (d[i]>0)?(left=0):(left = -d[i]);
    (d[i+n-1]<0)?(right=0):(right=d[i+n-1]);
    
    r[i]=fmin(2*left+right,2*right+left);
  
    }
  for(i=0;i<m-n+1;i++){
    if(r[i]<result)result=r[i];
  }
  printf("%d\n",result);
  
  free(d);
  return 0;
}