3 2
1 0 1
1 2
2 3
 10 10
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1
6 7
8 3
6 4
4 2
9 2
5 10
9 8
10 7
5 1
6 2

2
1
2
 0

import java.util.*;
import java.io.*;

public class d {
	
	public static StringTokenizer tok;
	
	public static void main(String[] args) throws Exception {
		
		BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in));
		tok = new StringTokenizer(stdin.readLine());
		int n = Integer.parseInt(tok.nextToken());
		int e = Integer.parseInt(tok.nextToken());
		
		boolean hasZero = false;
		boolean hasNegOne = false;
		int[] labels = new int[n];
		tok = new StringTokenizer(stdin.readLine());
		for (int i=0; i<n; i++) {
			labels[i] = Integer.parseInt(tok.nextToken());
			if (labels[i] == 0) hasZero = true;
			if (labels[i] == -1) hasNegOne = true;
		}
		
		if (hasZero || hasNegOne)
			System.out.println(0);
		else if (e > 0) {
			System.out.println(1);
			System.out.println(1);
		}
		else
			System.out.println(-1);
				
	}
}
