package no370;

import java.util.Arrays;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int k = sc.nextInt();
		int n = sc.nextInt();
		int[] d = new int[n];
		for(int i=0;i<n;i++) {
			d[i] = sc.nextInt();
		}
		Arrays.sort(d);
		int ans = Integer.MAX_VALUE;
		for(int i=0;i<=n-k;i++) {
			int left = d[i];
			int right = d[i+k-1];
			ans = Math.min(ans, Math.min(Math.abs(left), Math.abs(right)) + Math.abs(left - right));
		}
		System.out.println(ans);
	}

}