import java.io.IOException;
import java.util.Arrays;
import java.util.NoSuchElementException;

public class Main{
	static long dp[] = new long[51];
	public static void main(String[] args){
		
		FastScanner sc = new FastScanner();
		
		int K = sc.nextInt();
		int N = sc.nextInt();
		int[] x = new int[N];
		int[] L = new int[N+1];
		int[] R = new int[N+1];
		int l = 1;
		int r = 1;
		Arrays.fill(L, 123456789);
		L[0] = 0;
		R[0] = 0;
		for(int i=0;i<N;i++){
			x[i] = sc.nextInt();
		}
		Arrays.sort(x);
		for(int i=0;i<N;i++) {
			if(x[i] == 0) {
				K --;
			}else if(x[i]<0) {
				L[l] = 0 - x[i];
				
				l ++;
				
			}else {
				R[r] = x[i];
				
				r ++;
 
			}
		}
		
		
		
		Arrays.sort(L);
		int min = 400000000;
		int kyori = 0;
		for(int i=0;i<=K;i++) {
			if(i<l && K-i<r) {
				kyori = L[i] + R[K-i] + Math.min(L[i],R[K-i]);
				min = Math.min(min, kyori);
			}
		}
		if(min == 400000000) {
			min = 0;
		}
		System.out.println(min);
	}


	
}


class FastScanner {
    private final java.io.InputStream in = System.in;
    private final byte[] buffer = new byte[1024];
    private int ptr = 0;
    private int buflen = 0;
    private boolean hasNextByte() {
        if (ptr < buflen) {
            return true;
        }else{
            ptr = 0;
            try {
                buflen = in.read(buffer);
            } catch (IOException e) {
                e.printStackTrace();
            }
            if (buflen <= 0) {
                return false;
            }
        }
        return true;
    }
    private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
    private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
    private void skipUnprintable() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;}
    public boolean hasNext() { skipUnprintable(); return hasNextByte();}
    public String next() {
        if (!hasNext()) throw new NoSuchElementException();
        StringBuilder sb = new StringBuilder();
        int b = readByte();
        while(isPrintableChar(b)) {
            sb.appendCodePoint(b);
            b = readByte();
        }
        return sb.toString();
    }
    public long nextLong() {
        if (!hasNext()) throw new NoSuchElementException();
        long n = 0;
        boolean minus = false;
        int b = readByte();
        if (b == '-') {
            minus = true;
            b = readByte();
        }
        if (b < '0' || '9' < b) {
            throw new NumberFormatException();
        }
        while(true){
            if ('0' <= b && b <= '9') {
                n *= 10;
                n += b - '0';
            }else if(b == -1 || !isPrintableChar(b)){
                return (minus ? -n : n);
            }else{
                throw new NumberFormatException();
            }
            b = readByte();
        }
    }
    public int nextInt() {
        if (!hasNext()) throw new NoSuchElementException();
        long n = 0;
        boolean minus = false;
        int b = readByte();
        if (b == '-') {
            minus = true;
            b = readByte();
        }
        if (b < '0' || '9' < b) {
            throw new NumberFormatException();
        }
        while(true){
            if ('0' <= b && b <= '9') {
                n *= 10;
                n += b - '0';
            }else if(b == -1 || !isPrintableChar(b)){
                return (int) (minus ? -n : n);
            }else{
                throw new NumberFormatException();
            }
            b = readByte();
        }
    }
}