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 [] D = new int [M];
        for(int i=0; i<M; i++){
            D[i]=sc.nextInt();
        }
        Arrays.sort(D);
        int min=Integer.MAX_VALUE;
        int d = 0;
        for(int i=0; i<M-N; i++){
            if(D[i]<0 && D[i+N-1]<0 ){
                d=Math.abs(D[i]);
            }else if(D[i]>0 && D[i+N-1]>0 ){
                d=D[i+N-1];
            }else{
                int a = 2*D[i+N-1]-D[i];
                int b = D[i+N-1]-2*D[i];
                d=Math.min(a,b);
            }
            min=Math.min(min,d);
        }
        System.out.println(min);
    }
}