import java.util.*;

public class Main {
	public static void main (String[] args) {
    	Scanner sc = new Scanner(System.in);
    	int n = sc.nextInt();
    	int m = sc.nextInt();
    	int[] points = new int[m];
    	for (int i = 0; i < m; i++) {
    	    points[i] = sc.nextInt();
    	}
    	Arrays.sort(points);
    	int min = Integer.MAX_VALUE;
    	for (int i = 0; i + n <= m; i++) {
    	    int end = i + n - 1;
    	    if (points[i] * points[end] < 0) {
    	        min = Math.min(min, points[end] - points[i] + Math.min(-points[i], points[end]));
    	    } else {
    	        if (points[i] < 0) {
    	            min = Math.min(min, -points[i]);
    	        } else {
    	            min = Math.min(min, points[end]);
    	        }
    	    }
    	}
    	System.out.println(min);
	}
}