#include<iostream>
#include<algorithm>
#include<vector>
using namespace std;

int abs(int x){
	if(x<0)return -1*x;
	return x;
}

int main(){
	int n,m;
	cin>>n>>m;
	vector<int>data;
	for(int i=0;i<m;i++){
		int d;
		cin>>d;
		data.push_back(d);
	}
	sort(data.begin(),data.end());
	int ans=5000000;
	for(int i=0;i<data.size();i++){
		if(data[i]<0){
			if(i+n-1>=data.size())continue;
			else if(data[i+n-1]<=0)ans=min(ans,abs(0-data[i]));
			else ans=min(ans,abs(0-data[i])+abs(data[i+n-1]-data[i]));
		}
		else if(data[i]==0 && n==1)ans=0;
		else if(data[i]>0){
			if(i-n+1<0)continue;
			else if(data[i-n+1]>=0)ans=min(ans,data[i]);
			else ans=min(ans,data[i]+data[i]-data[i-n+1]);
		}
	}
	cout<<ans<<endl;
}