#include<iostream>
#include<algorithm>
using namespace std;
int n,a[1<<17],m;
main()
{
	cin>>n>>m;
	for(int i=0;i<m;i++)cin>>a[i];
	sort(a,a+m);
	int ans=1e9;
	for(int i=0;i<=m-n;i++)
	{
		int now;
		if(a[i+n-1]<0)now=-a[i];
		else if(a[i]>0)now=a[i+n-1];
		else now=a[i+n-1]-a[i]+min(a[i+n-1],-a[i]);
		ans=min(ans,now);
	}
	cout<<ans<<endl;
}