import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        try (Scanner scan = new Scanner(System.in)) {
            int n = Integer.parseInt(scan.next());
            int m = Integer.parseInt(scan.next());
            ArrayList<Integer> list = new ArrayList<>();
            
            int leftC = 0;
            int rightC = 0;
            for(int i=0; i<m; i++) {
                int v = Integer.parseInt(scan.next());
                if(v > 0) rightC ++;
                if(v < 0) leftC ++;
                list.add(v);
            }
            if( list.indexOf(new Integer(0)) < 0) {
                list.add(new Integer(0));
            } else {
                n--;
            }
            
            Collections.sort(list);
            
            int zeroIndex = list.indexOf(new Integer(0));
            int ans = Integer.MAX_VALUE;
            
            if(zeroIndex == 0) {
                ans = list.get(n);
            } else if(zeroIndex == m) {
                ans = Math.abs(list.get(zeroIndex-n));
            } else {
                for(int i=zeroIndex; i<list.size(); i++) {
                    if(i-n < 0) continue;
                    int right = i;
                    int left = right - n;
                    
                    int v1 = Math.abs(list.get(right)) * 2 + Math.abs(list.get(left));
                    int v2 = Math.abs(list.get(left)) * 2 + Math.abs(list.get(right));
                    ans = Math.min(ans, Math.min(v1, v2));
                }
            }
            System.out.println(ans);
        }
    }
}