using System;
using System.Collections.Generic;
using System.Linq;

class Program {
    static string ReadLine() { return Console.ReadLine(); }
    static int ReadInt() { return int.Parse(ReadLine()); }
    static int[] ReadInts() { return ReadLine().Split().Select(int.Parse).ToArray(); }
    static string[] ReadStrings() { return ReadLine().Split(); }

    static void Main() {
        var nm = ReadInts();
        int N = nm[0], M = nm[1];

        var ps = new List<int>();
        var ns = new List<int>();
        for (int i = 0; i < M; i++) {
            int x = ReadInt();
            if (x >= 0) {
                ps.Add(x);
            }
            else {
                ns.Add(-x);
            }
        }

        ps.Sort();
        ns.Sort();
        int ans = int.MaxValue;

        for (int i = 0; i < ps.Count; i++) {
            if (i >= N) break;

            int n = N - i - 1;
            if (ns.Count >= n) {
                if (i+1 == N) {
                    ans = Math.Min(ans, ps[i]);
                }
                else {
                    ans = Math.Min(ans, 2 * ps[i] + (n == 0 ? 0 : ns[n-1]));
                }
            }
        }

        for (int i = 0; i < ns.Count; i++) {
            if (i >= N) break;

            int n = N - i - 1;
            if (ps.Count >= n) {
                if (i+1 == N) {
                    ans = Math.Min(ans, ns[i]);
                }
                else {
                    ans = Math.Min(ans, 2 * ns[i] + (n == 0 ? 0 : ps[n-1]));
                }
            }
        }

        Console.WriteLine(ans);
    }
}