using static System.Math;
using System;

public class Hello
{
    public static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var n = int.Parse(line[0]);
        var m = int.Parse(line[1]);
        var a = new int[m];
        for (int i = 0; i < m; i++) a[i] =  int.Parse(Console.ReadLine().Trim());
        Array.Sort(a);
        var L = getAns(a, n);
        var ans = getAns2(a, L, n);
        Console.WriteLine(ans);

    }
    public static int getAns2 (int[] a, int L , int n)
    {
        var r = L + n - 1;
        var ans1 = a[r] - a[L];
        if (a[r] * a[L] >= 0) return  Max(Abs(a[L]), Abs(a[r]));
        else return ans1 + Min(Abs(a[L]), Abs(a[r]));
    }
    public static int getAns (int[] a , int n)
    {
        var m = a.Length;
        var minL = int.MaxValue;
        var mini = 0;
        for (int i = 0; i < m -n+1; i++)
        {
            var w = a[i + n - 1] - a[i];
            if (w < minL) { minL = w;  mini = i; }
        }
        return mini;
    }
}