import java.util.*;

public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		int d = sc.nextInt();
		int[] arr = new int[d + 1];
		for (int i = 0; i <= d; i++) {
		    arr[i] = sc.nextInt();
		}
		for (int i = d; i >= 3; i--) {
		    int x = arr[i];
		    arr[i - 2] += x;
		    arr[i] = 0;
		}
		if (arr[2] != 0) {
		    System.out.println(2);
		    System.out.println(arr[0] + " " + arr[1] + " " + arr[2]);
		} else if (arr[1] != 0) {
		    System.out.println(1);
		    System.out.println(arr[0] + " " + arr[1]);
		} else {
		    System.out.println(0);
		    System.out.println(arr[0]);
		}
   }
}