import java.util.*;
 

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] aa = new int[n+1];
		for(int i=n;i>=0;i--){
			aa[i]=sc.nextInt();
		}
		if(n<3){
			String g="";
			for(int i=n;i>=0;i--){
				g+=aa[i]+" ";
			}
			System.out.println(g.trim());
			return;
		}
		for(int i=0;i<=n-3;i++){
			int temp=aa[i];
			aa[i]=0;
			aa[i+2]-=-1*temp;
		}
		if(aa[n-2]!=0){
			System.out.println(2);
			System.out.println(aa[n]+" "+aa[n-1]+" "+aa[n-2]);
			return;
		}else if(aa[n-1]!=0){
			System.out.println(1);
			System.out.println(aa[n]+" "+aa[n-1]);
		}else{
			System.out.println(0);
			System.out.println(aa[n]);
		}
	}
}