import java.io.*;
import java.util.*;


public class Main_yukicoder370 {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Printer pr = new Printer(System.out);

        int n = sc.nextInt();
        int m = sc.nextInt();

        List<Integer> pp = new ArrayList<>();
        List<Integer> mm = new ArrayList<>();
        pp.add(0);
        mm.add(0);
        int zz = 0;
        for (int i = 0; i < m; i++) {
        	int d = sc.nextInt();

        	if (d > 0) {
        		pp.add(d);
        	} else if (d < 0) {
        		mm.add(-d);
        	} else {
        		zz++;
        	}
        }

        Collections.sort(pp);
        Collections.sort(mm);

        int min = Integer.MAX_VALUE;
        for (int i = 0; i < pp.size(); i++) {
        	for (int j = 0; j < mm.size(); j++) {
        		int tmp = zz;
        		if (tmp + i + j >= n) {
        			min = Math.min(min, pp.get(i) + 2 * mm.get(j));
        			min = Math.min(min, 2 * pp.get(i) + mm.get(j));
        		}
        	}
        }

        pr.println(min);

        pr.close();
        sc.close();
    }

	@SuppressWarnings("unused")
	private static class Scanner {
		BufferedReader br;
		Iterator<String> it;

		Scanner (InputStream in) {
			br = new BufferedReader(new InputStreamReader(in));
		}

		String next() throws RuntimeException  {
			try {
				if (it == null || !it.hasNext()) {
					it = Arrays.asList(br.readLine().split(" ")).iterator();
				}
				return it.next();
			} catch (IOException e) {
				throw new IllegalStateException();
			}
		}

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

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

		float nextFloat() throws RuntimeException {
			return Float.parseFloat(next());
		}

		double nextDouble() throws RuntimeException {
			return Double.parseDouble(next());
		}

		void close() {
			try {
				br.close();
			} catch (IOException e) {
//				throw new IllegalStateException();
			}
		}
	}

	private static class Printer extends PrintWriter {
		Printer(PrintStream out) {
			super(out);
		}
	}
}