import java.util.Scanner;

public class Main {

	static int max;

	public static void main (String[] args) {

		Scanner sc = new Scanner(System.in);

		max = sc.nextInt();
		int[] nums = new int[max + 1];

		for (int i = 0; i <= max; i++)
			nums[i] = sc.nextInt();

		int next = -1;
		for (int i = 0; i <= max; i++) {
			if (nums[i] != 0) {
				next = max - i;
				break;
			}
		}

		solve(next, nums);

		sc.close();

	}

	public static void solve (int d, int[] nums) {

		if (d < 3) {
			System.out.println(d);
			System.out.print(nums[max - d]);
			for (int i = max - d + 1; i <= max; i++)
				System.out.print(" " + nums[i]);
			return;
		}

		int i = 0;
		for (; i <= max; i++) {
			if (nums[i] != 0) {
				nums[i + 2] += nums[i];
				nums[i] = 0;
				break;
			}
		}

		int next = -1;
		for (int j = 0; j <= max; j++) {
			if (j == i || j == i + 2) continue;
			if (next == -1 && nums[j] != 0) next = max - j;
		}

		//System.out.println(Arrays.toString(nums));

		solve(next, nums);

	}

}