#include<bits/stdc++.h>
#define int long long
using namespace std;
const int mod=1e9+7;
int n,m,d[100005],fl,ans=2147483647;
signed main(){
//	freopen("clean.in","r",stdin);
//	freopen("clean.out","w",stdout);
	cin>>n>>m;
	for(int i=1;i<=m;i++) cin>>d[i];
	sort(d+1,d+1+m);d[0]=-1000000000;
	for(int i=1;i<=m;i++) if(d[i]>=0&&d[i-1]<0){fl=i;break;}
	for(int i=n;i>=0;i--){
//		cout<<d[fl+i-n]<<" "<<d[fl+i-1]<<"\n";
		if(fl+i-n<=0) break;
		if(fl+i-1>m) continue;
		if(d[fl+i-n]>0) ans=min(ans,d[fl+i-1]);
		else if(d[fl+i-1]<0) ans=min(ans,abs(d[fl+i-n]));
		else if(abs(d[fl+i-n])>abs(d[fl+i-1])) ans=min(ans,abs(d[fl+i-n])+abs(d[fl+i-1])*2);
		else ans=min(ans,abs(d[fl+i-n])*2+abs(d[fl+i-1]));
	}cout<<ans;
}
//fl+i-1
//fl+i-n
//-2 -1 1 2 3