import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.InputMismatchException;
import java.io.OutputStream;
import java.util.StringTokenizer;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.Map;
import java.util.ArrayList;
import java.util.List;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        Task solver = new Task();
        solver.solve(1, in, out);
        out.close();
    }

    static class Task {
        public void solve(int testNumber, InputReader in, PrintWriter out) {
            int N = in.nextInt();
            int M = in.nextInt();
            int D[] = new int[M];
            int plus=0;
            int minus=0;
            int PO[] = new int[M];
            int NE[] = new int[M];

            Arrays.fill(PO,1000000);
            Arrays.fill(NE,1000000);            

            for(int i=0; i<M; i++){
                D[i] = in.nextInt();
                if(D[i]>0){
                    PO[plus] = D[i];
                    plus++;
                }
                if(D[i]<0){
                    NE[minus] = -D[i];
                    minus++;
                }
                if(D[i]==0) N--;
            }
            Arrays.sort(NE);
            Arrays.sort(PO);
            int res=Math.min(NE[N-1],PO[N-1]);
            for(int k=0; k<=N-2; k++){
                if(PO[k]*2+NE[N-k-2]<res) res=PO[k]*2+NE[N-k-2];
                if(PO[k]+NE[N-k-2]*2<res) res=PO[k]+NE[N-k-2]*2;
            }
            out.println(res);



        }
    }

    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

        public long nextLong() {
            return Long.parseLong(next());
        }

    }
}