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

public class Main {
	public static void main(String[] args) {
		Scanner scn = new Scanner(System.in);
		int N = scn.nextInt();
		int M = scn.nextInt();
		int dp[] = new int[M];
		int ans = Integer.MAX_VALUE;

		
		for(int i=0; i<M; i++){
			dp[i] = scn.nextInt();
		}
		Arrays.sort(dp);		
		for(int i=0; i<M-N; i++){			
			 ans = Math.min(ans , Math.abs(dp[i]-dp[i+N-1]) +
					              Math.min(Math.abs(dp[i]), Math.abs(dp[i+N-1])));
		}
		System.out.println(ans);
	}
}