#include <bits/stdc++.h>
using namespace std;
int n,m,d[1005];
signed main()
{
	cin>>n>>m;
	for(int i=0;i<m;i++) cin>>d[i];
    sort(d,d+m);
    int minn=1e9;
    for(int i=0;i<m;i++)
	{
        int st=i+n-1;
        if(st>=m) break;
        for(int j=st;j<m;j++)
		{
            int l=d[i],r=d[j];
            int cur=(r-l)+min(abs(l),abs(r));
            minn=min(minn,cur);
        }
    }
    cout<<minn;
	return 0;
}